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Center ZOETa Environmental Guide forMahapr Seven U. S. Ports and .. ..r.~~~~~ . ,..~~~*:.'.:....... . :.:~~~~~~~.: . ::'.:'.~~~~~~ . .. 2 .2.. ...... ... ~ ~ ~ ~ ~ ....... A p p r o a c l~~~~~~~~~~~~~~~ l e s ........ ... ~~~~~~~~~~~~~~~ **~~~~...**:~~~~..... :... ...... Raritan Bay Offshore Sandy Hook DelaareBa Offshore Delaware Bay Galveson . ~ Mississippi Delta Prepared For: The President's Council on Environmental Quality QC *B73 aOcai an Atopei Ad n is ration C1 1972 netlDt evc AVG 13 a ~Environmental Guide forMahapr Seven U. S. Ports and Harbor Approaches R airitan Ba 2W~~ffhr Sandy Hook 2W........ By.. Offshore Delaware Bay COASTL $E'~CEENTER . ~ ~ $4 SOUTH ft ON ~~~AVENUE ....... $ABLETON C 29405-2413 COMPILED BY: W. A. BROWER .* .. ~.2. ...2 . ..2. . Galveston Mississippi lela D .SS ( ~~~~~~~~~~~~~~~R. G. QUAYLE Plrepared For: g fhe President's Council on Environmental Quality <'B, y: "-)CNational Oceanic and Atmospheric Administration ;;Environmental Data Service ,NUtQ National Climatic Center W~Asheville, N. C. Property 0t csc LibravytEBRUARY 1972 Table of Contents Page Abstract 1 List of Figures 2 List of Tables 3 List of Charts 4 Acknowledgement 5 Introduction 6 Data Sources and Definitions 7 Section One - General Description 9 Section Two - Area Summaries 17 Machiasport, Maine 18 New York (Two Areas) 35 Delaware (Two Areas) 58 Mississippi Delta 84 Galveston, Texas 101 Appendix A - Tropical Cyclones 117 Appendix B - Extratropical Cyclones 144 Bibliography 161 Abstract This report was compiled to aid in selecting suitable supertanker terminal sites for the United States. It presents climatological criteria necessary to assess the environmental effects on super- tankers at selected Gulf and East Coast ports. A general description of the major environmental controls governing the study area is followed by detailed analytical summaries for each port. List of Figures Fig. 1. Key map for supertanker port study areas. Fig. 2. Machiasport, Maine area map. Fig. 3. Tropical cyclone strike zone and probabilities for the Machiasport area. Fig. 4. New York and Delaware Bay area map. Fig. 5. Tropical cyclone strike zones and probabilities for the New York area. Fig. 6. New York and Delaware Bay area map. Fig. 7. Tropical cyclone strike zone and probabilities for the Delaware Bay area. Fig. 8. Persistence of waves of specified heights at Five Fathom Bank. Fig. 9. Mississippi Delta area map. Fig. 10. Tropical cyclone strike zones and probabilities for the Mississippi Delta area. Fig. 11. Galveston, Texas area map. Fig. 12. Tropical cyclone strike zone and probabilities for the Galveston area. List of Tables of Climatological Data Summaries Table 1. Machias, Maine (Land Station) Table 2. Eastport, Maine (Land Station) Table 2a. Comparison of Hurricanes and Northeasters in Northern New England Table 3. Environmental Data Summary; Machiasport, Maine Area Table 4. J. F. Kennedy International Airport, New York (Land Station) Table 5. Newark, New Jersey (Land Station) Table 6. New York City Office, New York (Land Station) Table 7. Environmental Data Summary; Raritan Bay Area Table 8. Environmental Data Summary; Offshore Sandy Hook Area Table 9. Dover, Delaware (Land Station) Table 10. Wilmington, Delaware (Land Station) Table 11. Atlantic City, New Jersey (Land Station) Table 12. Environmental Data Summary; Delaware Bay Area Table 13. Environmental Data Summary; Offshore Delaware Bay Area Table 14. New Orleans, Louisiana (Land Station) Table 15. Environmental Data Summary; Mississippi Delta Area Table 16. Galveston, Texas (Land Station) Table 17. Houston, Texas (Land Station) Table 18. Environmental Data Summary; Galveston, Texas Area 3 List of Charts Appendix A: Charts 1-12 Monthly Tropical Cyclone Movement Roses Appendix B: Charts 1-12 Monthly Average Extratropical Cyclone Tracks Charts 13-16 Seasonal Extratropical Cyclone Movement Roses 4iii�~ii . t . Acknowledgement Several members of the NCC staff assisted in producing this report. Without their help such a report would not have been possible. The National: Ocean Survey provided a great deal of information on tides and currents. The Naval Weather Service provided most of the support for the computer programming effort which made speedy summarization of large volumes of data possible. D. Lee Harris of the U.S. Army Coastal Engineering Research Center furnished information on coastal waves. Introduction For the purposes of this study, tank ships of 100,000 deadweight tons and more are considered to be "supertankers." The term was originally coined around 1950 to describe tankers of over about 28,000 deadweight tons. Deadweight tonnage is the weight (in long tons: 2240 lbs.) of cargo and fuel which a vessel is designed to carry safely. Currently the largest tankers are rated at about 326,000 deadweight tons which translates to about 90 million gallons of oil. Because of their size (over 1000 feet in length, nearly 200 feet in width) and draft (50-70 feet) U.S. ports cannot be economically dredged to accommodate the supertankers. it will be necessary, therefore, to construct new berthing facilities if such tankers are to call on U.S. ports, This report is designed to serve as a data base describing the existing environment of seven coastal areas. It may be used for planning, site selection and assessment of potential environmental impact. Section one describes the large scale features of the climate of the U.S. Gulf and East Coast. Section two provides the detailed statistics compiled for each study area separately,. Some repetition may occur from one study area to another. This is done so that any single area summary may be understood when read independently. Data Sources and Definitions The bibliography contains an alphabetical list of the primary data sources. It must be remembered that marine observations are taken by ships in passage. Since such ships tend to avoid bad weather whenever possible, a "good weather" bias may be introduced into the summaries. This problem has been partially overcome by relying on land and light station data as-well as synoptic weather maps for inferences regarding extreme conditions. Wind and waves are of paramount interest to most mariners. Several types of wind measurements are taken regularly. Among the most significant variables to consider are: 1) the height above the surface of the earth at which the measurements were taken, 2) the duration at or above a given wind speed. Sustained winds are those averaged over a period of about a minute. Peak gusts are relatively high wind speeds having a duration of less than a minute. In general a sustained wind may be multiplied by a factor of about 1.4 to estimate the peak gust during gusty weather. Unless otherwise specified, sustained winds are described in this report. An average height of 10 m above the surface is assumed. Most marine wind observations are estimated based on sea conditions, spray, etc. Waves are observed in two categories: Wind waves or seas are waves generated by the local winds in 7 the area of the observation. Swell waves are those which have moved beyond this area of origin. The higher of sea or swell was used in the summary. Observers note the significant waves on their observational forms. This is the approximate height of the highest one-third of all waves present. Higher waves may also exist. These are called extreme waves and they may be estimated by multiplying the significant wave height by 1.8. Unless otherwise specified, this report deals with significant waves. It must be kept in mind that water depth is a limiting factor for wave heights. Since point source data are rarely available in the marine environment data must be summarized for fairly large areas. Extreme wave heights may have to be adjusted depending on the actual water depth at the point of interest. Maximum wave heights will be somewhat less than this depth (except in the case of tsunami waves or storm surges). Tropical cyclones are cyclonic storms of tropical origin. There are two major types considered in this report: tropical storms which have wind speeds of 34 to 64 knots and hurricanes which have wind speeds equal to or greater than 64 knots. Two presentations are given. One deals with coastal strike zones (lines along the coast over which storms may pass), the other with penetration areas (areas within which a storm may occur). Detailed tropical cyclone statistics appear in Appendix A. Charts of extratropical cyclone tracks appear in Appendix B. 8 Section One General Description 9 Description of General Climate of the Northeastern U. S. Coast This region of interest covers the east coast of the U. S. ex- tending from the Delaware Bay area north to Eastport, Maine. This region, with its low elevation, lies within the zone of the Tprevailing westerlies." The climate and weather of this region is generally affected by masses of air originating in higher or lower latitudes and interacting to produce storm systems. The majority of air masses affecting this region belong to three types: (1) cold dry continental polar air that pours down from Canada, (2) warm moist air flowing northward over land from the Gulf of Mexico and from subtropical waters eastward in the Atlantic, and (3) cool damp air moving down from the North Atlantic. Thus, the basic climate results from an integrated effect of the various air mass systems. The Atlantic Ocean constitutes an important modify- ing influence, particularly on the immediate coast, but does not dominate the climate. Rapid and marked weather changes are charac- teristic of this section of the U. S. In the winter the cold dry northwest continental polar air moving down from Canada follows in the rear of cyclonic storms resulting in extremely cold temperatures. After the passage of one of these systems the weather is usually clear east of th e Appalachian, Adirondak and New England mountain barriers since the dry air sinks and warms. This northwest continental dry polar air also 10 brings cooling spells in the summer. The warmest weather in winter or summer is usually brought by southerly and southwesterly winds which bring warm moist air from the lower and warmer latitudes of the Gulf of Mexico. At times easterly winds from the waters of the Atlantic bring warm moist air to the eastern coastal region. The warmest weather in the sum- mer is influenced by the mean positioning of the semi-permanent subtropical Atlantic (Bermuda) high with its clockwise circulation between latitudes 320 to 35' N. and longitudes 40Q to 450 W. As the Bermuda high intensifies and extends westward, it tends to dominate the flow over the eastern section of the U. S. bringing warm moist tropical air inland. The resulting weather consists of scattered thundershowers, considerable daytime cloudiness and, at times, hot sultry conditions. Persistence of this high over the eastern U. S. frequently results in drought conditions as the dry subsiding air prevents the formation of precipitation. This high also exerts blocking actions on lows forcing them to travel across more northerly latitudes. Occasionally, in the summer, cool maritime polar air flowing on shore from the North Atlantic will tend to suppress Atlantic coastal thunderstorm activity and bring a relief from the warm temperatures. In late summer and fall this coastal area is sub- jected to tropical storms or hurricanes moving north from the Caribbean Sea and southwestern Atlantic. The damage by high tides is often severe whether the storm passes offshore or inland. Flooding caused by heavy rains is also asso- ciated with storms of a tropical origin. In winter and spring the northeast cyclonic winds along the North Atlantic coast are damp and chilly. Increased wintry precipita- tion and strong winds and tides result from coastal storms or "Northeasters." Easterly winds associated with cyclonic storms along the east coast advect air from the mild waters tending to raise coastal winter temperatures and lowering coastal summer temperatures compared to inland stations. Persistent dense fog along this coastal region is present as warm air over the water is advected inland over the cold land surface. The higher rela- tive humidities along the coast causes summer heat to be muggy and winter cold to be more raw and penetrating than inland. In the New England portion of the areas, summers are much cooler than in the more southerly areas. 12 Description of General Climate of the Central U. S. Gulf Coast This region of interest consists of the Gulf Coastal area extend- ing just east of the Mississippi Delta westward to Galveston, Texas. The climate of this region is broadly determined by the huge land mass lying to the north, its subtropic latitude, the Atlantic (Bermuda) High, and its proximity to the Gulf of Mexico. The Gulf principally influences the predominant year-round maritime tropical climate for this region. In winter, the area is subjected alternately to maritime tropical and polar continental air masses in periods of varying length. This region is usually south of the average track of winter cy- clones but occasionally one will move this far south. Westerly systems make their influence felt as cold fronts from the north- west which at times push southward into the Gulf of Mexico. The cold air behind these fronts, though modified by the southern journey, brings sudden and occasionally large drops in the temper- ature. The Gulf of Mexico, with its relatively warm waters, introduces a retarding effect upon cold fronts. As the invading cold air mass pushes out over the Gulf it moves against a strong flow of maritime tropical air in the opposite direction causing the front to become quasi-stationary. At these times the Northern Gulf area becomes a favored region for cyclogenesis. A wave usu- ally develops on the front in association with an eastward-moving 13 upper air trough. The principal track of the associated low center parallels the Gulf Coast or moves Inland producing per- sistent low stratus ceilings and rain in the Northern Gulf area. These conditions usually persist ahead of the low centers. The colder air masses in winter tend to gradually cool the sea sur- face temperatures offshore. This plays an important role in the formation of advection-radiation fogs in coastal areas from November-March and the formation of dense sea fog over the cold water surface. The low level direction of warm air above the sur- face near the coast determines where the fog will form. Snow seldom reaches this far south in winter. As spring arrives, these types of weather become less frequent. By May the semi-permanent subtropic Atlantic (Bermuda) high becomes well developed. Westerly storm systems are too weak to penetrate the strong ridge of high pressure extending westward across the Gulf of Mexico. The season is also too early for easterly systems to influence the Gulf coastal weather. Occasionally tropical dis- turbances and easterly waves will appear in the Gulf of Mexico by early summer. In summer the Bermuda high becomes very strong extending its anti- cyclonic influence over the Gulf. The prevailing southerly winds from the Gulf provide a rich source of moist tropical air which results in almost daily shower activity along the coast and near- shore waters of the northern Gulf. Air mass thundershower activity 14 increases during the day with the greatest activity in the after- noon. Summer rainfall is generally associated with southerly winds. When westerly to northerly winds occur in summer, periods of hotter and drier weather interrupt the moist semi-tropical climate of this coastal region. By August, easterly waves and tropical storms increase in the Gulf of Mexico and reach a peak in September. They begin to affect the weather in the Gulf with the principal paths of tropical storms into the Gulf coming from the straits of Florida and the Yucatan Channel. Over half of these tropical storms become hurricanes which bring their destructive force to both property and life along the coastal region. By mid fall the semi-permanent subtropic Atlantic (Bermuda) high begins its migratory movement eastward in the Atlantic. By November westerly systems begin their influence upon the weather in the Gulf and adjacent coastal regions. Advection and frontal fog make their appearance. The maritime tropical climate along this coastal region affords mild winters, cool springs, pleasant summers and warm autumns. POTENTIAL SUPERTANKER BERTHING FACILITIES :;ac:,:a..s...~.._.._ .~.. Rarita ayOffshore Sandy Hook Del r By Offshore Delaware Bay }alveston Fig. 1 Key map for supertanker port study areas. 16 Section Two Area Summaries f ~~~~~~~~~~~~17 MACHIASPORT, MAINE AREA General Description The coastline of the Machiasport area (see Fig. 2) is irreg- ular, rocky, and bold with numerous islands, bays, rivers, and coves. The larger bays afford excellent harbors and anchorage in adverse weather. The many boulders, rocks, and ledges along and off the coast, in many cases rising abruptly from deep water, make navigation somewhat difficult. Wrecks have occurred on practically all of the offlying islands and rocks between Portland and Machias Bay, most of them during bad weather. Spring tides (tides of in- creased range which occur about every two weeks when the moon is new or full) range from 11 to 21 feet along the coast. Numerous lights, both on the mainland and offshore islands, aid in navigation. Most of the principal light stations are equipped with radiobeacons and fog signals which are synchronized for dis- tance finding. Many coastal and harbor buoys are equipped with radar reflectors which greatly increase the range at which the buoys may be detected on the radarscope. Radar is an important navigation aid in the area due to the extended periods of low visibility. Machias Bay is the approach to Machias River and the towns of Machiasport and Machias. The bay is about six miles long and one to three miles wide, is easily entered day or night, and affords well-sheltered anchorage for large vessels. Libby Islands, lying in the middle of the two-mile-wide entrance, has a light tower 91 18 680 670 660 45 -..... 450 Machiasp............. ~~~Mach isot an 44 ~~~~~~~~~~~~~~~~~~~~0 430 430 680 670 660 Fig. 2 Machiasport, Maine area map. 1 9 feet above the water and is the principal guide to the entrance of Machias Bay. The extent to which the harbors of the area are closed to navigation by ice varies greatly in different years. During some winters most of the harbors are open while in others the only har- bors available for anchorages are Quoddy Narrows, Eastport, Little River, and Machias Bay. Portland Harbor generally has an open channel in all winters. THE ENVIRONMENT The Machiasport area lies in the region of most frequent move- ment of cyclonic storms. The region is in the general zone of west to east motion on which are superimposed northward and southward movements of large air masses from tropical and polar regions. The Labrador Current flows southward along the Nova Scotia coast. Branching to bring cold water in to the Gulf of Maine, it exerts a moderating influence on the immediate coastal and near offshore regions. The following sections describe the climatology of the Machiasport area. They are intended to give the overall climato- logical picture of the entire area. Pressure In the winter, the area lies between the Icelandic low- pressure area and the moderate North American continental high- pressure area, resulting in prevailing west-to-north winds in the coastal regions. In spring and early summer, as the two pressure 20 systems weaken, the Azores-Bermuda high intensifies and expands over most of the Atlantic Ocean. This extensive high pressure sy- stem shifts northward during the summer, with the center reaching 350 to 4Q0 latitude near mid-ocean in August and September, causing southwesterly prevailing winds in the Machiasport area. There are, however, great day-to-day variations in pressure, wind, and weather produced by migratory low- and high-pressure sy- stems which tend to be more intense and to move faster in winter than in summer. Since the area includes some of the paths most frequently traveled by these pressure systems, deviations from the mean pressure may be large, with consequent changes in wind and weather. The mean monthly atmospheric pressures, however, show small variation during the year, the normal level ranging from 1012 mil- libars in the late winter to 1017 millibars in the early fall season. Extratropical Cyclones As the Machiasport area lies along the paths most frequently followed by extratropical cyclones, the area experiences frequent wind shifts and rapid weather changes in the cooler seasons. These depressions generally enter the area from the west or from the southwest, the latter (Nor'easters) normally being of greater se- verity due to a considerable passage over water. Heavy rain or snow before the passage of the storm center may be extensive, and winds of hurricane force sometimes accompany then. After the storm center passes, the northwesterly winds, coming directly from the interior, are often bitterly cold. The classical "Nor'easter" (Northeastern or Northeast storm) is so called because winds over the coastal area are from the north- east. They may occur at any time but are most frequent and violent between September and April. They usually develop in the area 30- 40�N within about 100 miles of the coast and move north to north- eastward, attaining maximum intensity near New England and the Maritime Provinces. They nearly always bring precipitation and frequently bring gale force winds to the coastal area. Table 2a compares "Nor'easters" to storms of the tropical variety. Appendix B contains mean tracks and movement roses of extratropical cyclones. Tropical Cyclones Tropical cyclones, although much rarer than the extratropical variety, occasionally move northward in late summer and autumn. Fig. 3 gives the rather low strike probabilities for the Machias- port Coastal Zone. The storm centers generally move through the region in a north-eastward direction and, as a rule, are much more violent than the extratropical storms of the same season. Tropical cyclones tend to take on some characteristics of extratropical cy- clones before reaching the area, and are less intense than in more southerly latitudes. The table below reflects the frequency of tropical cyclones and hurricanes in the Machiasport study area 22 Characteristics Hurricanes Northeasters Climatology Origin Tropics, always over water Mostly Gulf of Mexico or South Atlantic regions, usually near 0 coast Season August-October October-April 0 Development Reach greatest intensity south Reach greatest intensity as they of New England and then diminish pass New England Frequency Average of 1 per 6 yr. 1-2 per yr. with surge __2.0 ft. Track Direction N to NE N to E Speed Avg. 36 kt.; range 29-48 Avg. 22 kt.; range 6-43 Pressures Central pressure Avg. 958 mb.; lowest 943 mb. Avg. 983 mb.; lowest 957 mb. Pressure pattern Usually symmetrical Usually asymmetrical IN) A Average storm diameter Small (400-600 n. mi.) Large (600-1500 n. mi.) Winds Maximum speeds 80-100 kt. not uncommon 70 kt. is rare Radius of maximum winds 22-66 n. mi., well-defined 90-340 n. mi., not well-defined, sometimes more than one Fetch lengths Short Long, 300-1400 n. mi. Surge Surge heights 3.7 ft. highest observed Up to 5.1 ft. observed Duration of high surge and strong wind 6-12 hr. 12 hr. to 3 days Inverted barometer effect May give important contribution Relatively unimportant con- to surge tribution to surge Topographical considerations Cape Cod protects northern New Little protection afforded England to some extent by Cape Cod 1000 950 90� 850 80� 750 700 650 500 50� 450 6? W - X 45' N-oo Yki 40 ( 40� CATEGORY MAXIMUM SUSTAINED WIND SPEED Cape MlyI TROPICAL CYCLONE GREATER THAN OR EQUAL TO 3_KNQTS _ HURRICANE GREATER THAN OR EQUAL TO 64_(N9TS INTENSE HURRICANE GREATER THAN OR EQUAL TO L9_NQI 3S5 35� 35� 3Q0 Neow Or'.,C 3Q( 30" 30' 25� 250 1 00 950 900 850 80� 75� 70� 650 AREA lachpasporL PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 13% 7 11 HURRICANE 5% 21 4 INTENSE HURRICANE <1% Fig. 3 Tropical cyclone strike zone and probabilities for the Machiasport area. 24 (as distinguished from the coastal zone analysis present in Fig. 3). Total Number Average Number of Years 1886 - 1971 between Occurrences Tropical Cyclones 9 10 Hurricanes 4 21 Of the total number of tropical cyclones (9) for the total period of record, there were 4 which reached hurricane intensity. Appendix A contains detailed information on tropical cyclones. Winds The prevailing westerly winds have a northerly component from November to March, with a southerly component from April to Oct- ober. Along the coast the general features of wind direction are similar to those over the water area except when modified by local topography. The windiest period coincides with the time prevailing winds have a northerly component. The highest frequency of gales (winds greater than or equal to 34 knots) also occurs during this time. Wind speeds over the open ocean areas approaching Machias- port are nearly always greater than the winds in harbor. Conse- quently, there may be twice the number of gales at sea. Hot sum- mer afternoons are frequently relieved by a refreshing wind blow- ing onshore from the cooler water. The effect of this sea breeze, however, seldom penetrates more than a few miles inland. 25 Extreme Winds As sufficient wind observations are unavailable for the region, both in time and space, the return values of maximum sustained winds given in the table below are based primarily on statistical methods by Thom (30). Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 67 kt 74 kt 85 kt 96 kt For example, on the average, there will be a maximum sustained wind speed of 85 knots in the Machiasport area once in every 25 years. Waves The distribution of high waves is roughly the same as that for the windiest period, as expected. Late Fall to early Spring are the seasons of maximum occurrence. There is a marked decrease in the average wave heights from April to September. The area has frequencies of high waves (greater than or equal to 12 ft) of over eight percent in March and November. There are some occurrences of waves greater than 20 feet for the same months. As with the winds, because there are insufficient observations for a climatological conclusion of significant wave heights, the table below primarily reflects the statistical method. Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 29 ft 35 ft 40 ft 44 ft Extreme Wave Height 52 ft 63 ft 72 ft 80 ft 26 Visibility Poor visibility may be produced by fog, haze, rain, and snow. Advection sea fog is the type most common along the coastal area. It occurs when warm humid air is cooled in passing over the cold ocean, usually during warmer months when the winds are from the south or southwest. This may, however, happen in any season. These fogs often set in almost without warning, and have been known to persist for three weeks with little interruption. The areas along the coast, at the heads of bays and within the rivers, are often comparatively clear while fog is very thick outside. Most land fog occurs in winter, and most sea fog occurs in summer. Steam fog (sea smoke), sometimes encountered in winter, forms in very cold weather when the air temperature is much lower than that of the water. Fog is more likely to form with light to moderate winds, as confirmed when comparing the percent fre- quency of fog with the mean winds in Table 3. The maximum number of days with fog occurs in July, the month having the lowest mean wind speed. The percentage frequency of reduced visibility also reaches a maximum during the summer months. With the onset of the stronger northwesterly winds, visibility improves. Temperature Summer temperatures in the Machiasport area are generally comfortably cool, with afternoon maxima occasionally in the low 70's. Days with readings of 90'F or more are rare. The June through August summer mean temperature average is about 55'F. 27 Winters average about 33'F in the Bay area. Days with O0F or lower have varied from four to 33 in a winter. Minima of 00F or lower seldom persist for more than a few days. In all seasons, changes in wind direction can cause large temperature fluctuations. In winter, southerly and southwesterly winds may bring mild weather, while northwesterly winds may be bitterly cold. In summer, warm weather occurs with southwesterly and westerly winds, and northeast winds may be cool and sometimes chilly. Temperatures at sea average about 4 to 8'F warmer in January, and 2 to 8'F cooler in July than along the coast. Precipitation Precipitation is relatively abundant and dependable throughout the year. Summer totals are somewhat less than in winter. Much summertime rain is from brief showers and thunderstorms, the latter being somewhat infrequent and occurring on the average-of less than 20 per year, mainly during the summer season. Over the sea their frequency and severity decrease. Seasonal snowfall is subject to wide variations from the aver- age, with 27 inches in 1952-3 to 132 inches in 1955-6 in Machias. Generally, the season for frozen precipitation runs from October through May, with the maximum occurring in February. Cloudiness Overcast conditions of 0.8 to 1.0 sky cover at the coastal stations range from about 55 to 60 percent in winter and from 30 28 to 40 percent in summer. Total cloud amounts measured at the coastal stations are fairly consistent with the sky cover at sea. In winter the amount will tend to become progressively greater downwind with winds between west and north. Summer brings a decrease in cloudiness while sky obscuration increases considerably. This occurs as the result of the combina- tion of weaker winds and greater number of days with fog. This is also reflected in the percentage frequency increase in reduced visibility. Relative Humidity Relative humidity is high throughout the year, and seasonal variations are small. Humidity is generally lower with winds from the continent and higher with southerly and easterly winds from the ocean. Therefore, maximum humidities are observed during the sum- mer months. Tides and Currents At Machiasport, Maine the spring tidal range is 14.4 feet; the mean range is 12.6 feet. The mean tide level is 6.3 feet. Currents are rather swift in the area and are summarized as follows: MAXIMUM CURRENTS LOCATION FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) Bay of Fundy Entrance 44�45'N 66�56;W 030 2.3 210 2.4 29 MAXIMUM CURRENTS LOCATION FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) 5 miles W of Brier Island 44013'N 66030'W 005 2.7 185 2.5 5 miles SE of Gannet Rock 44029'N 66041'W 040 2.6 230 3.9 7.6 miles SSE of Pond Point 44020'N 67030'W 015 0.5 215 1.2 Moosabec Reach (East) 44032'N 67034'W 110 1.0 260 1.0 The greatest storm surges in the Machiasport area result from the offshore passage of extratropical cyclones. Surges over five feet above mean high water have been experienced. 30 STATION: MACHIAS, MAINE POSITION: 44.7N 67.5W ELEVATION: 40 FEET MEANS AND EXTREMES FOR PERIOD 1940-1970 Temperature (eF) * Precipitation Totals (I-che) Mean number of days Means Extremes Snow, Sleet 5 - c ~~~~~ ~~~~~~~~~Max. Min. O'~~~~~~~~ 1'0 ' ZO P4 M .0 C o ~ .5A "0 - (a) 19 19 19 19 19 19 30 30 19 19 19 3019191919 JAN. 31.0 10.8 20.9 51 1953 -26 1961+ 1360 4.21 2.49 1958 20.9 44.7 1952 15.5 1956 8 0 15 30 7JAN. FEB. 32.3 11.1 21.7 50 1966+ -26 1961 1226 4.19 3.73 1951 19.6 40.0 1967 13.5 1955 7 0 13 27 7FEB. MAR. 39.1 21.2 30.3 64 1953 -12 1956 1068 3.68 2.26 1941 13.4 42,4 1956 8.0 1967- 7 0 528 1MAR. APR. 50.3 30.9 40.6 80 1957 7 1969 725 3.81 2.77 1954 2.2 9.7 1958 6.7 1957 8 0 *18 0AM. MAY 61.3 39.5 50.4 88 1959 23 1966 446 4.08 3.40 1961 .2 2.4 1963 2.4 196 3 8 0 0 5 0MAY JUNE 69.3 48.4 58.9 89 1963+ 32 1953 185 3.36 5.02 1942 0 0 0 6 0 0 * 0JUNE JULY 73.9 54.1 64.0 93 1968+ 37 1965+ 60 3.33 4.14 1948 0 0 0 6 * 0 0 0JULY AUG. 72.8 53.1 63.0 87 1961 34 1965 92 3.13 3.06 1951 0 0 0 6 0 0 0AUG. SEP. 65.6 46.4 56.0 89 1969 25 1965 270 4.01 4.02 1940 0 0 0 6 0 0 2 0SEP. OCT. 57.2 38.1 47.7 83 1963 18 i966 535 4.08 2.98 1952 .3 2.0 1969i 2.0 1965 7 0 0 9 0OCT. NOV. 46.3 29.6 38.0 70 1956 5 1951 803 6.06 2.68 1958 2.2 11.3 1962 6.0 1962 9 0 120 0NOV. DEC. 34.6 16.6 25.6 57 1962 -24 1951 1214 4.91 4.15 1950 16.6 43.5 1964 15.0 1964 8 0 13 28 3DEC. Year 52.8 33.3 43.1 93 Feb. 7584 4 52 J 7 15 5.5 Jan 86 * 47 167 is Year uly -26 + 79e4 &8.85 5.02 ln ig -26 1961+ 1942 1952 1956 (a) Average length of record, years. + Also on earlier dates, onths, or years. T Trace, an amount too small to measure. * Less than one half. ** Base 65�F Table 1 Land station climatological data summary for MACHIAS, MAINE. STATION: EASTPORT, MAINE POSITION: 44.9N 67.0W ELEVATION: 80 FEET MEANS AND EXREEMES FOR PERIOD OF RECORD 1931-196O** Temperature ('F) Precipitation Totals (Inrhes) Mean number of days H-nidlity ... Means Extremes 0T e m p eratures 4)o Max. Min Sune -P t N 0 5 u, a Os~~~0 - 0 "0 A 01 NO 5 00 N (a) 30 -30 30 30 30 30 30 30 30 30 30 30 38 30 30 30 71 71 71 30 67 65 34 65 59 63 J.. 30.6 11.1 22.9 18 -16 1303 4.11 2.47 18.0 53.7 16.8 8 0516 29 3 8 8 115 2 74 72 71 45 .9.6 J.. Feb 31.0 15.9 23.5 54 -22 1172 3.44 1.91 18.0 41.S 17.7 7 0515 27 2 8 7 13 * 274 70 71 15 6.2 Feb Sloe 37.4 24.2 30.8 76 -15 1037 3.68 1.93 12.7 25.7 10.7 7 085 26 * 5 9 14 * 3 75 69 73 52 6.3 9Jar Ap r47.0 33.2 40.1 51 10 742 3.50 2.21 6.4 27.8 18.3 7 (8 * 13 5 7 9 14 5 4 77 71 77 11 6.5 Apr M-ay 56-8 40.6 48.7 90 24 503 3.09 2.94 T 0.4 0.4 7 * 0 1 5 7 11 13 1 6 79 71 78 52 6.6 Ray Jun 64.4 47.2 13.8 92 36 279 3.55 2.81 I 5 5 7 * 5 5 5 6 12 12 3 5 82 75 81 54 6.6 J.. Jul 70.5 52.4 61.1 89 44 123 3.07 2.63 8 01 0 6 0 5 0 0 7 13 11 4 12 55 77 83 56 6.2 3.1s Aug 70.4 53.4 61.9 93 42 112 2.86 4.20 0 0 0 * 0 0 0 9 11 11 3 10 55 76 83 57 6.0 Aug Sep 64.0 49.3 56.7 92 33 253 3.53 3.66 a 0 0 6 * 8 0 0 9 9 12 1 6864 75 81 50 6.0 Sep Out 31.2 42.0 48.6 90 22 508 3.62 2.89 0.1 1.6 1.5 6 0 3 0 8 9 9 4 5 4 85 72 79 50 5.2 Out R.' 45.2 32.8 39.0 71 4 776 4.48 3.69 3.0 14.8 9.0 8a0 2 14 0 5 3 17 * 2 90 75 76 38 7.2 Ray Sec 34.0 19.5 26.8 60 -23 1182 3.74 3.15 10.7 35.2 12.0 8 012 27 2 7 5 16 * 5 77 73 75 40 6.9 Eec 93 -23 4.20 5 3.7 19.5 Year 10.5 35.5 43.0 A.g. DE-n 8010 42.67 Aug. 66.9 J... Apr. 82 *53 140 7 89 1141t62 14 60 79 73 77 31 6.4 Year 1949 1933 1943 1952 1946 (a) Average length of record, years. + Also on later dates, months or years. T Trace, an amount too small to measure. *Less than one half. 5*See Station HisisrY Table 2 Land station cilimatological data summary for EASTPORT, MAINE. 31 ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Machiasport, Maine ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 3 4 3 3 2 1 2 3 2 3 4 3 3 Mean 21.3 19.9 17.9 14.7 13.5 11.3 9.8 10.8 11.7 15.0 18.4 21.9 15.5 99% S 46 47 45 40 34 30 29 31 32 39 47 47 40 Maximum observed (1871 - 1971) Extreme winds of over 100 knots are knovn to have occurred during Northeasters. > 34 Knots (% freq.) 12.4 10.0 8.9 3.6 2.2 0.3 0.4 0.3 0.6 3.9 8.6 15.3 5.5 > 41 Knots (% freq.) 2.8 2.7 1.3 1.0 0.3 0.0 0.0 0.0 0.0 0.1 1.1 2.4 1.0 Prevailing direction NW NW NW SW SW SW SW SW SW SW NW NW SW WAVES (FEET) 01% 1 1 00 0 0 0 0 0 0 0 0 < Mean 5 5 4 3 3 2 2 2 2 3 4 5 3 99% < 17 18 13 10 10 9 8 8 10 10 14 18 12 > 12 Feet (% freq.) 4.0 1.4 9.6 0.0 0.0 0.0 0.0 0.0 0.0 0.0 9.1 2.1 2.2 > 20 Feet (% freq.) + + + 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + + + VISIBILITY (% FREQ.) Visibility <� N. mile 2.9 2.3 5.9 6.5 9.4 14.4 27.8 22.2 10.4 7.3 4.1 6.4 10.0 Visibility <1 N. mile 4.2 3.6 8.7 7.7 10.2 17.5 32.3 25.9 12.6 8.7 5.3 8.6 12.2 Visibility <2 N. miles 6.9 7.5 12.7 11.2 13.2 22.8 38.3 31.7 15.7 13.4 7.9 14.0 16.4 Visibility <5 N. miles 18.6 18.5 19.1 17.4 21.6 33.9 49.4 44.1 23.3 19.7 15.8 25.4 25.7 Visibility <10 N. miles 44.4 39.1 39.6 41.6 39.7 56.0 67.7 60.7 40.6 45.9 41.0 51.8 47.5 + - less than 0.05% Table. 3 Environmental data summary; Machiasport, Maine area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Machiasport, Maine ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 3.5 0.8 5.8 9.3 13.8 25.2 38.7 34.7 14.9 10.4 6.3 4.7 14.0 Mean number of hours operation of fog signals * 105 84 87 91 135 196 290 271 140 94 72 85 1650 Maximum number of hours operation of fog signals for any year (annual only)* 2364 WEATHER & CLOUDS (% FREQ.) Precipitation 13.6 16.2 14.2 10.6 11.3 8.4 5.8 6.8 8.7 9.4 13.9 22.4 11.8 Freezing precipitation 0.0 0.2 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 0.1 Frozen precipitation 10.1 13.4 8.8 3.4 0.2 0.0 0.0 0.0 0.0 0.3 3.0 14.3 4.4 Thunder & lightning 0.0 0.0 0.0 0.0 0.0 0.3 0.2 0.2 0.2 0.0 0.0 0.0 0.1 Sky 52/8 24.3 24.5 30.1 33.9 30.4 28.2 34.7 38.4 42.7 30.8 13.8 18.3 29.2 Sky overcast (8/8) 34.0 29.8 26.8 20.0 17.3 14.7 12.5 13.4 14.0 18.9 31.2 35.0 22.3 Sky obscured 2.8 3.4 5.8 7.5 9.5. 11.2 17.9 17.4 8.5 5.8 4.3 5.6 8.3 Low cloud overcast 23.3 22.2 19.4 16.5 13.7 12.5 10.2 10.2 12.1 15.9 22.6 26.9 17.1 Mean cloud cover (eighths) 5.4 5.1 4.9 4.6 4.7 4.7 4.3 4.1 4.0 4.6 5.8 5.8 4.8 AIR TEMPERATURE (OF) Minimum -5 -2 14 21 33 42 46 47 44 32 12 0 -5 01% 5 5 2 16 26 36 43 48 50 46 34 25 8 28 Mean 28.2 27.4 33.7 39.0 45.4 51.7 56.6 58.0 55.2 49.7 41.9 31.8 43.7 99% < 44 44 46 50 57 63 68 72 66 60 55 50 56 Maximum 59 47 57 63 64 73 78 84 70 84 60 55 84 5 32 �F (% freq.) 64.6 50.3 38.0 7.1 0.0 0.0 0.0 0.0 0.0 0.0 9.1 56.3 18.8 85 �F (% freq.) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 * Libby Islands fog signal Table 3 Continued. ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Machiasport, Maine ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 79 78 78 80 84 87 89 89 83 79 77 79 82 SEA TEMPERATURE (�F) Minimum 27 27 27 31 32 37 39 44 42 34 36 32 27 o1% S 30 29 31 32 35 39 43 45 46 44 41 35 38 Mean 39.8 37.0 36.2 37.6 42.1 46.5 50.5 53.1 52.0 50.2 47.7 43.3 44.6 99% S 50 50 48 52 57 66 71 74 70 65 58 54 60 Maximum 56 54 52 56 62 76 76 84 76 76 64 60 84 SALINITY (%o) Minimum 28.9 28.9 29.1 28.9 29.1 29.0 30.6 31.1 31.1 31.4 30.6 29.4 28.9 Mean 32.1 32.0 31.9 31.5 31.4 31.6 32.0 32.3 32.5 32.5 32.4 32.1 32.'0 Maximum 33.5 33.5 33.2 32.7 33.1 32.9 33.6 33.7 34.4 34.0 34.1 33.7 34.4 DENSITY (p) Mean (at)* 23.8 23.7 23.7 23.3 23.2 23.5 23.8 24.0 24.1 24.2 24.0 23.8 23.8 SEA-LEVEL PRESSURE (mb) Minimum 975 976 967 980 992 995 994 996 988 973 976 978 967 01% < 980 981 984 988 996 1000 1001 1000 997 989- 985 985 991 Mean 1013 1012 1013 1015 1015 1014 1015 1014 1017 1017 1015 1014 1014 99% � 1038 1042 1036 1035 1032 1028 1026 1027 1031 1033 1037 1033 1033 Maximum 1041 1044 1045 1040 1043 1031 1028 1034 1035 1038 1039 1041 1045 * at - (p - 1) X 103; p - gm cm'3 Table 3 Continued NEW YORK AREA General Description The coastal regions of the New York area (see Fig. 4) are generally flat and sandy, having very low elevation above mean sea level. The area presents problems of unusual difficulty to the mariner due to the offlying shoals, strong and variable currents, large amounts of fog, and turbulence of wind and sea in the great storms that so frequently sweep it. A great volume of waterborne commerce also moves through the area to and from the Port of New York. The approach to New York and Raritan Bays from sea is gener- ally along the south coast of Long Island or the east coast of New Jersey. Ambrose Channel Light, equipped with a fog signal and a radio beacon, marks the entrance to Ambrose Channel, the principal deep water passage extending from the sea to the deep water of Lower New York Bay. Sandy Hook Light, the oldest light in continuous use in the United States (established in 1764), marks a secondary, southerly route from the sea to Lower Bay and to Raritan Bay. Raritan Bay, with depths of seven to 18 feet, is full of shoals and has a mean tidal range of about 5 feet. Sandy Hook Bay, the southern part of Lower Bay, affords excellent anchorage as the shoaling is gradual, the bottom is good holding ground, and the depths of water range from 15 to 30 feet. The mean tidal range is 4.6 feet. 35 760 750 740 730 41" 410 Raritan Ray ~? Offshore Sandy Hook 40 ...... Wmgon~ Dj Delaware Inside of CapeMa e May39 0 Five Fathom Bank Offshore Delaware Bay 380? 380 76" 750 740 730 Fig. 4 New York and Delaware Bay area map. 36 Only during extremely severe winters will the main channels be restricted by ice, and then only for short periods of time. Near the outer extremities of Sandy Hook, at the western end of the Ambrose Channel entrance, the flood current attains a veloc- ity of about 2 knots. The ebb tide in Lower Bay is generally stronger than the flood by 10% or more. At the seaward end of Ambrose Channel the velocity of the flood current is 1.7 knots and the ebb current is 2.3 knots. The important currents affecting navigation in the approach to the New York and Raritan Bays are those due to winds. The largest current velocity likely to occur under storm conditions is 1.5 knots. A sudden reversal in the direction of the wind produces a corresponding change in the current, either diminishing or aug- menting the velocity. Offshore and away from the influence of the tidal flow into and out of the larger bays, the tidal current maintains an approxi- mately uniform velocity, generally less than 0.3 knots. Shifting its direction continuously to the right, it sets all directions of the compass during each tidal cycle of 12.4 hours. THE ENVIRONMENT The New York area lies in the "prevailing westerly belt" of the middle latitudes on the east coast or leeward side of the con- tinent. The daily weather, which makes up the climatic pattern, moves generally from west to east; consequently, the region is in- 37 fluenced more by land mass to the west than by the ocean to the east. The proximity of the ocean, nevertheless, influences the winds, temperature, and precipitation enough to modify the typical continental regime. Therefore, the climate on all but the outlying islands can best be described as modified continental. Superimposed on the general westerly circulation are the fre- quent wind shifts and changes in weather associated with extratro- pical cyclones. In the winter, the area lies within the heart of the belt traversed by these storms. As a result, changes of wind, temperature, and clouds are frequently abrupt and conditions are generally variable. In summer and fall tropical cyclones can bring stormy weather, although most of these storms assume extratropical characteristics by the time they reach the northern latitudes. A principal area of storm formation is off the Middle Atlantic coast. Extratropical storms spawned in this area during the cooler months generally move northward or northeastward toward New England and New York. These coastal storms may, on occasion, produce strong winds and heavy precipitation. The cold Labrador Current which flows parallel to the coast- line, and the warm Gulf stream farther eastward, exert considerable influence on the climate. The cooling of warm moist air brought northward by the prevailing southwesterlies during the warm months causes fog which reaches the approaches to New York. From November through April prevailing winds are from the NW; for the remainder of the year, SW. Gales with wind velocities of 38 34 knots or more are predominately from the NW. There are also many from the NE. Pressure During the winter, the New York area is sandwiched between the Icelandic Low and the North American Continental High, which results in a pressure pattern producing the prevailing northwesterly winds in the colder months. As the two pressure systems weaken in the spring, the Bermuda High intensifies; and by summer, it covers the Northeastern States, producing the prevailing southwest winds of the warmer months. There is little seasonal variation in the mean pressure, which ranges from a high of about 1019 millibars in late fall and early winter to a low of about 1014 millibars in late spring. There are, however, great day-to-day variations in these means, primarily due to the numerous cyclones and anticyclones that traverse the area. Daily variations are much greater in winter than in summer. Occasionally, large variations are experienced when a tropical cyclone passes through in late summer or fall. Extratropical Cyclones In winter, the center of the mean tracks followed by extra- tropical cyclones traverses the New York area. Consequently, there are frequent shifts from the prevailing westerlies and rapid changes in weather. Usually the cyclones enter the area from the west, passing through the northeastern states, or they move from the southwest with the center offshore. 39 The coastal storms which move northeastward (Nor'easters) are likely to be of greater severity from having passed over consider- able water. Before the storm center passes, it may bring heavy rain or snow. Strong winds, sometimes of hurricane force, accom- pany it. The northwesterly winds in the western half of the storm, having come directly from the interior of the cold continent, will often be bitterly cold. The Machiasport narrative contains a detailed description of "Nor'easters." Appendix B contains extratropical cyclone tracks and movement roses. Tropical Cyclones Tropical cyclones occasionally move northward into the area in late summer or autumn. The storm centers generally move through the region on northeastward courses toward Nova Scotia or over the adjacent ocean. Some severe hurricanes have moved northward across Long Island, with reported wind speeds of 70 to 80 knots. As a rule, these tropical storms are much more violent than the extra- tropical storms of the same season. Many of them take on some extratropical characteristics prior to reaching the area and are less intense than in more southerly latitudes. The table below reflects the frequency of tropical cyclones and hurricanes for the New York area. Total Number Average Number of Years 1886 - 1971 between Occurrences Tropical Cyclones 11 8 Hurricanes 4 21 40 Of the total number of tropical cyclones (11) for the total period of record, there were 4 which were of hurricane intensity. Appendix A contains detailed information of tropical cyclones for the study area. A summary of tropical cyclones for the two New York strike zones is presented in Figure 5. Winds From October to March, the prevailing winds over the New York area are between west and north. After March until the summer regime is established, the wind is variable. From June through September the prevailing winds are southerly. Winds are stronger from November through March; and in the warmer months, May through August, the winds are the weakest. However, the summertime pre- vailing southerlies are more persistent than the wintertime north- westerlies, because of the lack of extratropical cyclone acitivity during the warmer months. The summer period, at times, is dis- turbed by -tropical cyclones and severe thunderstorms. In general, the wind regime in the Raritan Bay area is similar to that east of Sandy Hook. The average wind speeds in Raritan Bay are generally less, owing to the increased friction caused by the surrounding land mass. At the coastal stations, the hot summer afternoons often are relieved by a refreshing sea breeze blowing onshore from the cooler waters adjacent to the coast. This breeze seldom penetrates more than 10 miles inland. 41 100� 950 90� 85� 80" 75� 70� 650 50� 500 450 W Mocolopar 450 New Yo k 40� 40� CATEGORY MAXIMUM SUSTAINED WIND SPEED Cp TROPICAL CYCLONE GREATER THAN OR EQUAL TO 34_NISOS HURRICANE GREATER THAN OR EQUAL TO 64..END-TS INTENSE HURRICANE GREATER THAN OR EQUAL TO L0ANQIS 35� 35� 30� i , / s300 avso. Nw Orlea C 30 250 250 1000 95� 90� 850 800 : 75* 70� 650 AREA New York Zone I PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 1% 85 1 HURRICANE 1% 85 1 INTENSE HURRICANE <1% AREA New York Zone 2 PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 11 % 9 9 HURRICANE 6% 17 5 INTENSE HURRICANE <1% - Fig. 5 Tropical cyclone strike zones and probabilities for the New York area. 42 Gales (greater than or equal to 34 knots) are encountered in about 2 to 4 percent of the observations during winter. They are more frequent with westerly or northwesterly winds. Gales are rare in summer, but may be encountered in tropical cyclones or in thunderstorms. Extreme Winds As there are insufficient wind observations for the area, both in time and space, the return values of maximum sustained winds, given in the table below, are estimated with the aid of statistical methods. OFF SANDY HOOK Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 74 kts 81 kts 90 kts 99 kts RARITAN BAY Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 69 kts 76 kts 85 kts 92 kts For example, on the average, there will be a maximum sustained wind speed of 81 knots east of Sandy Hook once in every 10 years. Waves Distribution of high waves is roughly the same as that for the windiest period. September to March are the months of maximum occurrence. The maximum frequency of waves equal to or greater than 12 feet also occurs during these months. However, Raritan Bay, sandwiched between New Jersey and New York, has significantly fewer waves of such height. Heights greater than 20 feet are rarely 43 observed in the Bay, while occurrences are more common off the coast of Sandy Hook. As with the winds, because there are insufficient observations for a climatological conclusion of a significant wave height, the tables below primarily reflect a statistical estimate. OFF SANDY HOOK Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 37 ft 41 ft 47 ft 53 ft Extreme Wave Height 67 ft 74 ft 85 ft 96 ft RARITAN BAY Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max Significant Wave Ht. 11 ft 14 ft 17 ft 19 ft Extreme Wave Height 20 ft 25 ft 30 ft 35 ft Visibility Although fog, haze, rain, and snow are all causes of poor visi- bility, in the New York area, visibility at sea and in the Bay area is most commonly restricted by advection fog. This type of fog occurs most frequently in late spring and early summer when the winds are from south to southwest and the warm humid air is cooled to its dew- point by the cold Labrador Current. During the summer months there is an increase in observations reporting restricted visibility. This frequency increases on approaching the Bay area. A partial explana- tion is the decrease in winds as the Bay area is approached and the resulting enhancement of conditions conducive to the development of fog. Steam fog occasionally forms during very cold weather when the air temperature is much lower than that of the water. However, it is usually quite shallow. 44 Tepeature The maritime influence affects temperatures. In spring and summer the sea breeze tends to reduce temperatures, but in winter, when the water temperatures are warmer than those of land, the * ~~opposite occurs. In any season, a change in wind direction can cause a large fluctuation in temperature. In winter, southerly and southwesterly winds may bring in mild weather, while north- westerly winds bring in extreme cold. In summertime, southwesterly and westerly winds will be warming, but northeast winds may be cooling and sometimes chilly. Readings in the coastal area rarely exceed 100'F and the 90'F level is reached on only 1/3 to 1/2 of the days during the summer. Air' temperatures off Sandy Hook are warmer than over Raritan Bay during the winter months because of warmer sea temperatures and less continental effect. Precipitation Precipitation over the coastal sections is moderately heavy. Normal monthly totals vary from minima of 2.5 to 3.0 inches in February or October to maxima of 4.5 to 6.0 inches in August. An- nual totals range from 41 to 45 inches. Showers and thunderstorms, which provide most of the rainfall from May through September, are localized and tend to be "spotty."1 Thunderstorms come most frequently in the late afternoon and evening and usually are brief. However, rainfall from thunderstorms can be very intense and may seriously restrict visibility at sea. Thunder- 45 storms occur in the New York area on an average of 30 days per year, mostly during June, July, and August. Their frequency and severity decrease over the ocean, as does the annual percent fre- quency of total precipitation. Cloudiness At sea in winter, overcast skies and clear skies (cloud amount less than or equal to 2/8) are each recorded on about 35 percent of the observations. The summer conditions are a little better, with about 26 percent of the observations showing overcast and 37 percent clear skies. Over Raritan Bay, overcast conditions range from, about 36 to 44 percent in winter and about 30 percent in summer. Relative Humidity In the New York area throughout the year, relative humidity is rather high with annual early morning averages from 70 to 80 per- cent, and evening averages from 60 to 80 percent-. There is some seasonal variation', with highest readings during the summer months. Humidity variations, like temperature fluctuations, are dependent on the wind patterns. Humidities in the Raritan Bay area are higher with onshore winds, but usually a few percent lowger than humidities seaward off Sandy Hook. Tides and Currents'- Offshore Sandy Hook The spring tide range at Sandy Hook is 5.6 feet with a mean range of 4.6 feet. The mean tide level is 2.3 feet. The currents may be summarized as follows: 46 MAXIIMUM CURRENTS LOCATION FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) 1.7 miles ENE of the N. Tip of Sandy Hook 40�30'N 73�59TW 295 1.5 100 1.7 0.4 mile W of the N. Tip of Sandy Hook Channel 40�29'N 74�01'W 235 2.0 50 1.6 Rotary tidal currents are experienced on a semi-diurnal basis. The following data are from about .2 mile west of Sandy Hook Approach Lighted Horn Buoy 2A, 40�27'N 73�55'W: TIDAL CURRENTS Hours after max. flood at the Narrows, Dir. Speed New York Harbor (deg) (kts) 0 313 0.4 1 325 0.3 2 356 0.2 3 055 0.2 4 094 0.3 5 118 0.4 6 136 0.6 7 147 0.5 8 177 0.2 9 256 0.2 10 290 0.3 11 298 0.4 Storm surges in the New York area can result from either tro- pical or extratropical cyclones. The highest observed storm surges have been about 10 feet above mean high water. The highest surges are associated with hurricanes. 47 Tides and Currents - Raritan Bay At all stations in Raritan Bay, spring tidal ranges are less than six feet and currents less than one knot. At Atlantic Highlands (40�25tN, 74�02'W) the spring tidal range is 5.7 feet; mean tidal range is 4.7 feet and mean tide level is 2.3 feet. M4AXIMUM CURRENTS LOCATION FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) 2 miles W of Sandy Hook Point 40�29'N 74�04'W 265 0.6 085 0.6 Storm surges often enter Raritan Bay as the result of tropical or extratropical cyclone passages, the highest being the result of hurricanes. Surges of nearly ten feet above mean high water have been recorded. 48 STATION: J. F. KENNEDY INT'L. AIRPORT, NEW YORK POSITION: 40.7N 73.8W ELEVATION: 13 FEET NORMALS, MEANS, AND EXTREMES Temperaur Precipitation Relative Wind M . number of days humidity Mm ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~07 131 5~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0. P .2 (h (.) (h(.0 0 0 h h 23 03 23 1- 12 1 2 9 9 9 0 91uco1 212 1 2121 2 F 385 247 31 12 19 2. 293 9 3 5 293 481962 3 6 a199 2 5 319 6 9 9 199 69 12 3 9 46 125 912 12 12 12 12 12 12 3 6 2 9 45.9 31.4 38.7 72 1963 7 1967 918 4.12 7.95 1953 1. 35 1966 2.27 1962 8.2 21.1 1960 9.1 1967 70 71 87 64 13.6 41 510 1966 6.0 8a10 13 12 2 1 3 0 1 15 0 A 57.5 40. 49. 82 1964+ 261969* a8 3.48 6.6 1964 1.2 1963 1.79 1969 0.1 1.41965 14 1965 71713 6612.8 44 26 1970 6.2 7 10 15 1 2 .3 II 0 2 0 M 6 9.5 80.9 601.2, 99 1969 34'1966, 167 3.7 6.14 191 03 95 288 I 196 T T 1967 T 1967 76705 6711.7 35 24 1969* 6.2 7 15 it 11 0 3 3 1 I 0 4N J79.3 60.9 70.1 99 1964 45 1967 12 3.35. 4.27192 7~ 119)49 1.81 19968 0.0 0.0 0.0 79 73 59 71 10.9 32 30 1967 6. 7 11 12 9 0 4 4 3 8 0 0 1 934.7 67.1 75.9 104 1966 85 1963 0 4.04 8.48 1969 0.46 1954 3.21 1969 0.0 0.0 0.0 78 74 57 71 10.6 37 34 1969 6.2 6 12 13 9 0 9 3 4 0 0 0 A 92.9 66.0 74.5 97 1969 46 1965 0 4.97 17.41 1955 0.87 19964 6.859 1955 0.0 0.0 0.0 78 76 57 71 la.4 46 30 1965 5.9 7 13 tt 9 0 5 a a 0 0 0 5 76.2 59.3 67 .8 94 1961 40 1963 36 4.16 9.60 1960 5.70 1931 5.8 90 00 0000 7 85 01. 40 30 1970 I. 1 9 1 2 1 1 0 0 0 a 65.9 49.3 57.6 84 1967, 25 1961 248 3.21 6.41 19586 0.09 11963 3.21 1966 TZ 0.5 1962 a.5 1962 72 77 533 68 11.2 39 26 11967 8.1 13 9 la 7 3 1 3 0 0 1 0 M 93.2 39.1 46.2 73 1968+ 20 1967 564 3.51 7.89 1963 1.30 9~49 2.93 1963 0. 2.1 1967 2.1 1967 737258 68 12.3 44 03 198 64 81 1 16 11 * 1 2 0 0 6 0 8 41.3 28.4 34.9 68 1962 5 1962 93 .25 .6 1969 I.72 195 8 2.05 1968 6. 16419 60 8.3 1960 71 73 61 661.I6 0 99I. 8 9 1 1 2 * 3 0 5 2 JUL. FEB. AUG. JUN. !' AUG. FE6B. FEB. I A N M9 61.1 45.3 83.2 104 1966 .2 1963 5219 43.93 17.41I1955; T 1949 6.8 1955 27.9 253196 19.9 1969 74 73 57 6,7 12.0 5 2 26 19 66 6.0 97 120 149 118 8 23 32 10 21 93 * 0 For the period J-n 1961 through the current yeor. tt Lonuno nf reod, yearn, bae .. Jaur data, tttUs uhois Indioatdt dtm.nstanul ..ft. used to rbts b.Ullttnaei opeauet degrees.1 F.; & Ftgeea, Inatead of lesse . tnadtros oto-Ind..t i dlret. o tn r... or degree frum ton Neh; Othe muoh. may be o mr f fete ynurs I0 Y rcllrrn. tnlotn snmft h.. Inbn.ad moemntI mlepetou;anrestehmd Le., 00-.. Eat 8 Sooth, 27- West, 30-North, and 00-C. Rabs. OsloR. Mand Is tbe vetor- enf rhere hv bee breabs. In she reod. tn perent Heardng degree day -.I.l are lb. aum of negattve feerrnn vrg aly tempera- band dteecrte ssd speeds divided by the number of ob-ervton. If ftgreu appear Is Use dsnoos ,b) Clmlgtct utandard normal f1931-1960f. tune fro F3 . CoolIng degree dytalarshsusuprtndasraofvrgedly cabinsr unde "Fsts -I... Ftbe .1 cureaeln speeds achatstuueed1, tur aus Lus th.. -n ball. -espraee Irom 0 5- F. Sleet -a Incladd Issemfl toral begnstng sft0 Juty 1948, Tbn ""c + Also noorirdts" ntho ee.lepllets.. Y . tnclodea so11d aroma atta I..es an-1 d putolen. cunnlttn of ann pelnta nnoaad 7MIrson ana-on -pu. smllt mouue, d n tblotpro c. ay fnedcstuhlrul/merns,$ Greatest calendar day through Motch 1969. Tbe prvIln dterln Lc ld In the Neesnala Sky "ouvee In eaprsso taeagof Otu Ino clods-rohcun phenomen to 10 foe complete sky Grlceatest calendar day August 1966 through March 1969. M..... ..nd Esemstble Is Irom cecords tbeoub cnvr. Th. obeu la dapa Is based onavrae todlnna 0-3, partly oloady days 4-7,..ad 1963. cloudy days 8- 10 mtetb, * 707' at Alanka .sttu - ---bb.d.n.l ~ df. d-i. .f h gl dreores ose gram calor pee oqoar vensmosr. Table 4 Land station climatological data summary for J. F. KENNEDY INTERNATIONAL AIRPORT, NEW YORK STATION: NEWARK, NEW JERSEY POSITION: 40.7N 74.2W ELEVATION: 7 FEET NORMALS, MEANS, AND EXTREMES Tempertur P-eipiftusn etbu Wind &iMean number of days humidity in - 0 suaset~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~o--- * n ot~~~~~~~~~~~~~~~~~~~~~~0 07 13 190 0, meu ~ . o~ a "n -i o,.5 ~~~~~~ ~~~5o 5 . 1 7 1 - 1 29 n9 b29 53 u a. � 226 22 22m mm o5292noy9-9-9.95 5 M 48 8 ~ ~ ~320 17 198167 17 6 4 9 629 29 4 968 3 196 2. 60 5 176157 b9 So 12 25 29 23 27 292992 3 3 39 ..5 25. 02.3 68.167 1. 1968 41014 33 5.1 196 I0.81 13 1.7 1962 71 2. 161 1. 1961 65 71 57 62 11. 9 5 23191 6. F 40.7 24.7 52.7 59 1967 4 1967 904 2.80 4.47 1906 1.22 1968 2.48 1961 8.1 25.4 1967 20.0 1961 66 69 33 39 11.7 NW 46 23 1965 8.3 71 8 13 10 24 *195 4. .6 47 2 10.3 23 0 48.8 32.1 40.3 79 1~~968 I8 16 70 4.9 .2 1954 11 196 2.3 199 . 26. 193 17. 195 669 31 3 12. NW 43 27 190 61 8 9 4 1 0 1 30 A 60.9 41.7 51.3 88 ~~~~1969 38069 4121 231 I 6.4 10 0.90 1964 2.1 1 93 0.3.1 1 9I56 4.1 195 666 47 33 1.3 S" 02 91 6. 4 1 1 1 0961 8721 51.9 620 9 99 35 9 17 26 6.28 16 5.2 1964 .1 1968 T 1936 T 15 69 66 05 023 03 95 64 7 1 5 l 0 0 81el.3 6b.2 71. 3 lb 1966 49 1967 9 a.44 4.37 1966 0.49 1966 1.75 19680 0.0 0.0 0.0 74 72 03 349 9.4 SW 05 07 1932 6.0 7 11 12 1003 1 3 0 0 0 J 86.1 66.5 76.3 105 1966~ 59 1969+ 0 3.67 17.9 1961 0.89 19966 3.1 196 00 .0.0 73 72 33 61 8. 8 SW 45 18 19050 6.2 7 12 13 15 0 6 1 7 0, 0 0 A 28 64.9 74.4 95 1968+ 50 1965 5 .311.84 15 0.0 96 417 199 00 . . 7 33 60 8.7 56 46 09 1933 59 a 12 11 90 4 1 6 0 0 01 S 77. 37.6 67.3 94 1970+ 42 1965 39 3.76 7.86 1966 1.50 1964 471 96 0. 0000 757326 9. W 1 0390 34 11 8 1 8021 2 0 0 0 0D a 66. 47.056.6 87 1967 28 1969 276 3.11 6.75 1953 0.21 1963 2.65 196 To 0.3 1932 0 . 3 1952 75 77 531 624 9.4~ 5W 48 1 194 0. 12 8 1 80 12 0 0 1 0 N 33.3 ~~~~~~~~~~37.3 45.4 76 1968 20 1967 38 33 368 1963 1.48 1963 2.59 196 3 0.5 3.1 1967 3.1 1967 74 78 39 67 10.2 SW 82 09 1935 6.2 a a 14 10 *It 220 0 0 042.0 27.4 34.7 68 1966 81968 939 3.2a2 3.74 1957 0.27 1955 1.9 0 1968 7.9 29.1 1947 26.0 1947 73 73 61 67 10.9 SW 33 So 1962 6.2 9 a 14 I1 I a 2 0a 2 JIUL.6' IJA'N. AUG.7 ' OCT. SEP. DEC. D EC. NOV. YR 62.7 44.8 53.7 105316 1196 57 43.38 11. 84 1953 0.21 1963 4.71 1966 29.7 29. 11947 26.0 1947 71 72 34 61 10.3 SW 82 09 1950 6.1 99 112 134 122 a 25 21I 20 20 93 0 0 For period Junoe 1965 through curet year. Mean. and extreme nbove are from oxintiog nod coparable minpuourmo. Ann entremI havo boon exceeded at other niten in the Il...lity as follows:. Lowest temperature -14 in February 1934; mmimum monthly premdpltatlon 22.48 in August 1943; minioom~ .monthly precipitation 0.07 iso Jtate 1949. (a) Lrnnih of --ouo year, ha.. d no ....uy dut. Unlena tn.iheoa tedioud, dimoaionl unit. aard inhi hub.tIn Irn Itemeatr in degren P.;- & Piguorn Irasd nf Iec...a-In dreon .I.. o tomeidiate ditmeul In neo of dgeafoa oe ot Other .-nh. may be foemren fewor vua i preotptruno.~ inciudg snowfall, in inh ind momet I.s L.dc. Pnr 6=nn; and relaion humidity L... 09-Rant, it - Seuth. 27 - Weste.3 b- N..h and 00- Calm. Resabam wied-in'the enomNo S of thees Acn been berh intercrin peren. Sleulg degre day .I .anu 0 th. a-m of nenailn depatn-en af a-eua daily tempea- wind di-ocio. and speeda dinided by h. nuber of nhe-aln ffgee peri the dirIctIns (hi Ciutatntngoal stadard nanl 191-19601. - om from 65' F. Cnoieg degree day taul, -ate dinnam of peattin departre of enrge daily column under "Pnt ml" the ..Ponorndieg apndn ace fanneno nhnevr -m evae. * Lena than ... half. seperum-e Iro 05' F. Steer wo Inclded in teefiltoal bentning with laby 1948 Th. tee + Al.. noerle date.. rnorh.'n er.'r p.eta- incldna Ionld gruIna of ieInl. t an. .d l.WIar.ce onnlIlg nf see pellets en-ed T Toner, Inamun too nmai Inmuue. thin layer of -IceIeav fng rd.edan "6elblti to 1/4 mile no lean. Theop peulin ieton fo wind Sky -hNrml, by corer ... rreed Inarag of 0 for no roda no nhncaIg pheeemne to 16 for nrplete sky M..oI, und Emoemen taleI foam o-oda through -nner Th. nmber et nlea days Is base d On u-erageclondl.es 0-3, . peI, olnady dya 4-7. and 1963. olnudy daya 0- 15 onothe, O ; 70' at Alakas stationa. Slar radiation dt.ata e the uoeraoenfdirntand diffun. radiation n hortattl nnfc Th. langly Table 5 Land station climatological data summary for NEWARK, NEW JERSEY. STATION: NEW YORK CITY OFFICE POSITION: 40.8N 74.0W ELEVATION: 132 FEET NORMALS, MEANS, AND EXTREMES Relative M ... .. Mean nu fa days Tempra~tur Precipitati.a humidity wn Et-~~~~~~~~~~~~~~~~~~~~m a.t- a un____n0snstaHn ii.- ti - 0 sO~~~~~~~~~~~~~~~E 01 07 1319 n aa a ei -2 e ma a a S'au . * - a0' - 0.a a.-- 'a V 0 570~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~i -0e i~P24 4- n~ r'a8u a a m fr.8~~~ ~~~~~~~~ M9 2 2 Sr is R- 1* aM , . , -N Z:, um a- . () (6) (h) (b) 101 101 (b) (6) 101 101 58 101 101 101 B 8e5 50so50 50 45 23 23 93 42 42 42 42 101 99 9 5 6 56 36 56 42 393 2.9 1. 72 1950 1691582 986 3.1 7.94 1912 0.77 19535 3.33 1915 7.6 27.4 11925 13.2 1935 65 688 60 61 10.9 NNW 47 NW 1959, 50 6.0 8a9 14 11 2 * a 32 * 33 N 47. 33.2 40.5 86 195 5 872 70 4.1 8.7 187 0.901885 4.25 876 .4 305 186 18. 1940641615578 11.4NW S NW 980 7a5.7 9 12 12 15 2 1 1 13 0 29 N~ ~~~~~~~~~~~~~~~~~~. 71. 534 6. 916 219 1 .7 .110 .010 .816 7 196 7 194 701536 9.NW 384 1976237 4 19 1 10 0 * 0 4 1 80. 6. 714 101 196 4418 9 3.3 is7 19300 1949 4.74 184 00 00 . 37 5 61 8. W 49S 1950 657 5.6 W1 01 77 85.3 68.2 ~~~~~76. 0 96 52 194 0 3.701.9 89049 90 336 90 00 0.0 I . 737 66 . W 4 NW 199 63. 813 101 04 6 0 0 046 A 83. 66. 75. 104 918 0 195+ 0 4.44 0.8619550.24 964 .80 909 .0 0. 0.0 78 7 58 6 7.8SW 3 NE 954 605.49 12 109id 0 49 6 0 0 0939 O 9: 76.8 60.1 68512158911 0 38168 18 .118 .018 . .. 7 79 57 67 8. 1 2 SWW 4 E16 352 1 1 3 o 66.3 30.3 38.3 94 1941 28 1936 233 3.4 13.31 1903 0.14 1965 11.17 1903 7 0. 192590.8 1925 71 76 4536259.196W 40 N51955+ 62 4.9 12410 91860 19 *6S * 0 24 7N 33.7 4. 47. 84 195 7 175 0 340 .9 99 18 .0131 38 93 1. 9019 10.0 198 97 96 01 NW 7 NE aI0 5308 0 12 9 1 0 1 49,1 4 2. ,2. 03.9 70146 -1 11 929.2 .5 13602I195 .1 907 62 296 94 6.9147 6 6a6 660.7N 4 W 96+ 05. 9 9 3 107 5 0 519 * 1 JUL.~ ~~~~~~~~~~ ~~~~~~~~~~~~ F4B 3FF JUN OCT. 9 AR DEC NOWV. II . Y9 . 62.2 46.7 54. 10 196 -5 21934 487 42.67 16.85 198 0.0 1949 1.7103 39.9 30. 196 26. 194 707 6 62 9. NW 7 NE 195 895617I2 3 121 8 18 16 0 8 0 Men andntee abv are fro ematn 4n 1952rbl 6mours Anua 6at n hav bea ex e at 4te stsi h oalt nflos Maw~~wan monthly snowfall 37.9~~~ inhsnFanry19;fsetnbowid13 rmteSEnOcbr154 Mat 2egha ead erbsda asr aa itu sems ntaedmelntatr udt bsblei r:smeaueI ere . 9lan 9nso at Ieter 9in a dintu 03am tats di94rt9 4le an4 of deger from sca Noth Ote mo0tb 6may 71e fur 1966 n ar fewer yer9f cuytuta tuotg nmaiI nue;medmv9etI llupnhoe ndrltunhmdiy Iea0 at,1-Sot,2-Ws,36 us, e 0Cam eatormidt4se63ara sbr itou hen breaks te16 13 65 the 4. ed tn penant Hearing degre day 9usi see4 shel ama, n6 negtiv deatn at ueag dol 75peo 75e Str.re 63d up7d 7ie SW the NWme 194 aberts it fige oypua tn) the dteu4 � Aba as arlier daes, mseeh. ur year. "inn peinra" inuadau tall gnatea a tue tetert and puiolet uaututina ofsnow pe~eneruaard a Ta S nom9us67ptt2txtW only I: T6an an amnue 104 sml amuae NastElaentieHavfgrdua nhiiyi/meuret Belam anna remyararuena ~ ~ ~ ~ 9 0 Nr prue hy. a mlo sign,4 Th rutle iesn tar9 60nd 6e 3h Hur12a Sh 387n ta nanen tea rang 2I Star4 na 8i8od or nbautg phnmaat t u2upe h 66ans and. Eusrem3 sable 1954 29a 1936rd 2he33 saver. Th3 number at nicue d7y ir 0 Taa an2. 7ve1g 76onu iS 62rti ulodSWy 4-7 and56 49 1 9 7 964. utaud NWy 0-t NEnths. .8 9 1 0 * 5 4 33 403 47 : sO 9lantru statana Sata ruda9i 9da03ra11" . 9019 . 886 96 6 5N 3N are2 shr uvrgudr9rn d99us 13lua an 2 nturtnraa Th l9angley 1 29 7 35 9 0 94 1 902 3.26 7.53 193urau2an1955a 3.eab909 6er aqu6r1947a 26.4e1947 JU;FSP U;OTabl 29 05M264 Land staio 72atlgia 56t 6umr for 9 NEW YORK 1IT OFFCE NEW YORK ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Raritan Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 2 2 2 3 2 1 1 2 2 2 2 3 2 Mean 11.4 11.5 12.2 11.4 10.0 9.7 9.2 8.8 9.4 9.7 10.5 10.9 10.4 99% S 35 32 32 36 32 28 31 29 28 34 31 31 32 Maximum observed (1871 - 1971) Winds near 100 knots have probably occurred during the passage of Tropical Cyclones. 2�34 Knots (% freq.) 1.2 0.1 0.1 1.3 + + + + 0.1 1.3 0.1 + 0.4 _ 41 Knots (% freq.) + + + + + + 0.0 0.0 + + 0.1 + + Prevailing direction WNW NW NW NW S S S S S S SW WSW WSW S WAVES (FEET) 01% S 0 0 0 0 0 0 0 0 0 0 0 0 0 Mean 3 3 3 2 2 2 2 2 3 2 2 2 2 99% S 9 8 8 8 8 5 6 8 7 6 8 6 7 2 12 Feet (% freq.) + + + + + 0.0 0.0 0.0 + + + 0.0 + 2 20 Feet (% freq.) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + 0.0 + VISIBILITY (% FREQ.) Visibility <4 N. mile 2.5 2.2 1.4 1.8 1.7 1.4 0.7 0.5 0.4 0.9 1.2 1.7 1.4 Visibility <1 N. mile 4.4 3.7 3.2 3.0 2.9 2.4 1.3 1.1 1.0 1.7 2.2 3.4 2.5 Visibility <2 N. miles 7.4 7.1 5.3 4.8 5.3 4.9 3.5 3.0 2.7 3.3 4.4 6.4 4.9 Visibility <5 N. miles 22.1 20.6 15.0 14.8 17.4 18.9 19.3 19.5 14.3 16.6 17.9 21.1 18.1 Visibility <10 N. miles 51.4 46.5 39.1 40.5 42.4 49.0 53.9 51.8 42.8 44.6 45.8 53.5 46.8 + - less than 0.05% Table. 7 Environmental data summary; Raritan Bay area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Raritan Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 11.5 11.3 10.7 11.2 11.2 10.0 7.0 7.8 6.5 7.0 9.0 11.2 9.5 Mean number of hours operation of fog signals * 40 34 29 40 45 43 29 18 17 22 29 34 380 Maximum number of hours operation of fog signals for any year (annual only)* 578 WEATHER & CLOUDS (% FREQ.) Precipitation 15.0 15.1 16.4 14.9 11.3 7.9 6.9 7.5 7.9 8.7 11.2 14.5 11.4 Freezing precipitation 0.6 0.4 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.2 0.1 Frozen precipitation 4.8 5.5 4.8 0.6 + + 0.0 0.0 0.0 0.1 0.7 3.8 1.7 Thunder & lightning 0.0 0.0 0.1 0.2 0.6 0.6 1.1 0.7 0.3 0.1 0.0 0.0 0.3 Sky <2/8 35.9 36.9 38.2 33.7 33.2 37.0 36.0 38.4 43.7 47.2 40.4 38.9 38.3 Sky overcast (8/8) 44.1 42.0 40.6 40.3 37.0 30.7 28.9 29.7 28.7 29.6 36.3 40.1 35.6 J ln Sky obscured 9.9 15.4 11.2 13.8 20.9 15.8 11.0 8.9 4.0 4.4 3.0 4.8 10.0 Low cloud overcast 24.2 22.0 22.8 19.2 16.0 14.5 15.3 13.6 14.8 14.9 20.4 22.3 18.4 Mean cloud cover (eighths) 4.8 4.7 4.6 4.9 4.8 4.5 4.6 4.4 4.1 3.8 4.4 4.6 4.5 AIR TEMPERATURE (�F) Minimum -6 -15 3 12 31 44 52 46 39 25 5 -13 -15 01% S 12 11 21 30 45 55 61 61 53 39 27 16 36 Mean 33.6 33.5 40.0 49.8 59.9 69.4 75.1 73.9 67.5 57.8 47.3 36.5 54.0 99% 5 49 47 61 69 79 83 88 87 83 73 62 51 70 Maximum 72 75 86 92 99 101 106 104 102 94 84 70 106 S 32 �F (% freq.) 62.7 67.1 42.6 5.8 0.1 0.0 0.0 0.0 0.0 0.3 14.0 52.6 20.4 > 85 0F (% freq.) 0.0 0.0 + + 0.5 0.9 6.8 3.7 0.3 + 0.0 0.0 1.0 * West Bank fog Signal + - less than 0.05% Table 7 Continued. ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Raritan Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 69 67 67 68 70 71 72 73 72 70 69 69 70 SEA TEMPERATURE (�F) Minimum 28 27 27 35 46 51 63 65 56 41 32 28 27 01% < 29 29 33 38 49 54 64 67 59 51 42 32 45 Mean 38.5 37.0 39.6 46.3 55.3 65.2 71.8 72.9 69.3 60.7 51.8 43.1 54.3 99% S 50 52 54 59 72 78 80 82 81 72 61 53 66 Maximum 54 56 59 64 81 83 85 87 86 78 67 63 87 SALINITY (%o) Minimum 5.6 10.1 4.2 1.7 2.0 3.9 11.4 11.6 5.9 7.5 9.9 5.6 1.7 Mean 22.0 22.5 20.2 19.1 20.8 22.7 24.5 24.8 25.0 24.8 23.7 22.8 22.7 Maximum 28.6 29.3 28.4 28.1 28.0 29.3 30.7 30.2 31.2 32.9 29.1 31.1 32.9 DENSITY (p) Mean (at)* 16.3 16.5 14.8 14.0 15.2 16.6 17.9 18.3 18.4 18.3 17.4 16.8 16.7 SEA-LEVEL PRESSURE (mb) Minimum 978 971 983 985 ' 995 992 994 977 992 995 989 983 971 01% _ 992 983 990 991 1000 1002 1001 1002 1001 999 992 993 996 Mean 1016 1016 1015 1015 1014 1014 1015 1015 1018 1018 1018 1019 1016 99% S 1039 1040 1035 1034 1030 1031 1031 1029 1034 1036 1039 1040 1035 Maximum 1042 1042 1041 1035 1032 1035 1032 1032 1037 1040 1041 1041 1042 * t = (p - 1) X 103; p = gm cm-3 Table 7 Continued. ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Offshore Sandy Hook ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 3 3 2 3 2 1 1 2 2 2 3 4 2 Mean 14.4 14.3 13.6 12.7 10.6 9.9 9.2 9.2 10.6 11.9 14.3 14.9 12.1 99% S 46 43 46 39 32 28 31 30 32 39 40 40 37 Maximum observed (1871 - 1971) Winds in excess of 100 knots have been Iecorded in Hurricanes and Northeasters. 2-34 Knots (% freq.) 3.3 2.5 3.2 1.5 0.3 0.1 0.1 0.3 0.4 1.2 2.4 3.9 1.6 > 41 Knots (% freq.) 1.2 1.1 1.2 0.3 0.1 0.0 0.0 0.1 0.1 0.5 1.0 1.0 0.6 Prevailing direction NW NW NW NW SW S S SW S NW NW NW NW WAVES (FEET) o1% S 0 0 0 0 0 0 0 0 0 0 0 1 <j Mean 3 3 3 3 2 3 2 2 3 3 3 4 3 99% S 16 15 12 10 10 8 9 10 12 12 15 13 12 > 12 Feet (% freq.) 1.2 2.4 2.9 0.5 0.2 0.0 0.2 0.0 1.6 1.2 1.4 2.2 1.2 > 20 Feet (% freq.) + + 0.8 0.0 0.0 0.0 0.2 0.0 0.3 0.0 0.3 + 0.1 VISIBILITY (% FREQ.) Visibility <j N. mile 5.0 4.4 2.7 6.9 9.3 5.8 5.6 2.3 2.3 1.8 1.5 0.7 4.0 Visibility <1 N. mile 8.7 7.0 6.2 8.6 11.9 8.3 6.3 4.6 3.7 3.6 2.4 2.1 6.1 Visibility <2 N. miles 11.8 12.9 8.1 11.1 14.5 13.1 9.5 6.6 4.6 5.1 5.4 3.7 8.9 Visibility <5 N. miles 17.6 22.8 15.0 18.8 22.8 26.6 20.6 19.3 9.8 10.3 8.7 8.1 16.7 Visibility <10 N. miles 44.7 48.6 39.6 39.9 55.6 58.9 58.5 49.9 42.7 43.6 44.2 41.2 47.2 + = less than 0.05% Table. 8 Environmental data summary; Offshore Sandy Hook area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Offshore Sandy Hook ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 8.4 8.0 9.4 11.9 20.3 20.1 15.0 10.8 8.9 9.0 3.9 5.3 10.9 Mean number of hours operation of fog signals * 75 72 75 74 91 81 73 59 51 42 44 57 794 Maximum number of hours operation of fog signals for any year (annual only)* 1169 WEATHER & CLOUDS (% FREQ.) Precipitation 10.9 12.2 11.1 12.2 6.7 5.6 6.9 5.3 8.9 9.1 11.9 10.5 9.3 Freezing precipitation 0.1 0.1 0.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.6 0.1 Frozen precipitation 5.6 5.0 2.7 0.7 0.2 0.0 0.0 0.0 0.0 0.0 0.0 1.3 1.3 Thunder & lightning 0.0 0.0 0.1 0.2 0.5 0.8 1.3 1.5 0.9 0.2 0.5 0.0 0.5 Sky 22/8 34.0 36.7 38.8 34.5 35.0 39.0 35.1 37.7 43.1 44.6 34.3 33.2 37.2 Sky overcast (8/8) 34.5 33.4 31.6 31.3 25.8 22.5 27.9 27.2 26.3 24.6 33.1 32.3 29.3 Sky obscured 8.3 12.8 7.4 8.3 12.5 11,8 8.0 7.3 2.4 2.9 1.4 2.2 7.1 Low cloud overcast 21.6 18.5 19,6 16.2 19.2 14.0 16.0 12.0 12.7 14.7 20.8 25�0 17.4 Mean cloud cover (eighths) 4.5 4.3 4.4 4.6 4.7 4.4 4.5 4.0 4,0 4.3 4.7 4.7 4.4 AIR TEMPERATURE (�F) Minimum 5 -1 17 27 36 48 54 53 50 39 16 7 -1 01% S 11 14 23 35 43 54 61 63 53 42 29 18 37 Mean 34.7 35.3 39.6 47.2 56.0 65.6 72�3 72.9 67.7 59.2 49.9 39.7 53.2 99% 5 54 53 55 63 72 80 84 84 80 73 64 58 68 Maximum 64 61 72 75 85 88 90 90 89 88 70 68 90 S 32 �F (% freq.) 45.7 31.0 10.4 0.1 0.0 0.0 0.0 0.0 0.0 0.0 2.3 20.8 9.2 >85 �F (% freq.) 0.0 0.0 0.0 0.0 0.1 0.2 1.0 0.7 + + 0.0 0.0 0.2 * Ambrose fog signal + = less than 0.05% Table 8 Continued. ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Offshore Sandy Hook ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 85 84 80 79 82 84 83 82 80 79 79 80 81 SEA TEMPERATURE (�F) Minimum 30 27 27 35 40 45 51 56 52 46 42 30 27 01% < 31 29 31 37 41 49 59 62 58 51 44 36 44 Mean 39.9 38.2 39.7 44.3 52.2 62.4 69.7 71.6 68.1 60.9 53.6 47.0 53.9 99% < 56 56 55 57 68 74 78 80 79 72 64 59 67 Maximum 60 60 60 62 76 84 84 82 84 78 70 70 84 SALINITY (%o) Minimum 13.2 10.5 12.8 11.4 10.3 13.6 17.9 17.7 18.6 12.8 14.4 14.6 10.3 Mean 22.6 22.9 21.4 20.3 21.8 23.8 25.5 25.6 25.8 25.6 24.7 23.7 23.6 Maximum 28.6 29.3 28.4 28.1 28.0 29.3 30.7 30.2 31.2 32.9 29.1 31.1 32.9 DENSITY (p) Mean (Ct)* 16.4 17.1 15.3 15.0 15.9 16.9 18.3 18.5 18.6 18.6 17.9 17.5 17.2 SEA-LEVEL PRESSURE (mb) Minimum 975 980 977 981 996 998 952 977 987 993 989 983 952 01% < 991 987 990 993 999 1002 1002 1003 1001 998 992 992 996 Mean 1016 1017 1015 1014 1015 1015 1016 1016 1018 1019 1016 1017 1016 99% < 1035 1038 1035 1032 1031 1021 1027 1028 1032 1035 1033 1034 1032 Maximum 1040 1041 1053 1041 1038 1035 1032 1032 1037 1038 1039 1041 1053 * t - (p - 1) X 103; p - gm cm-3 Table 8 Continued. DELAWARE AREA General Description The area covered in this section is generally low and flat. Long stretches of sandy beaches and tidewater marshes characterize the New Jersey and Delaware ocean coasts, while the shores of Dela- ware Bay are mostly low with few conspicuous marks other than lights. The principal dangers along the Atlantic coastal region are the outlying sand shoals, the fogs, and the doubtful direction and velocity of the currents after heavy gales. Gales from the north- east to southeast cause heavy breakers along the coast and outlying shoals. Such dangers have produced many wrecks. Traffic is heavy along this coast and a sharp lookout must be kept-to avoid collision. Deep-draft vessels should stay outside of Barnegat Lighted Horn Buoy B and Five Fathom Bank Lightship between New York Harbor and Delaware Bay. Depths as little as seven fathoms are found as far as 13 miles from the Atlantic shore. Depths inside the 20- fathom curve, about 25 miles off Delaware Bay, are irregular, and in thick weather a deep-draft vessel should not approach the coast until sure of its position. Tides range from 3.5 to 4.5 feet along this section of the Atlantic coast. Five Fathom Bank Lightship, located about 20 miles seaward of the Delaware Bay entrance, is the only remaining lightship along this section of the coast. The ship is equipped with fog signal and a radiobeacon, and its light is 63 feet above the water. Tidal currents in its vicinity average 0.2 knots. 58 760 750 740 730 410 -- ................................ 410 .. ....... .... ............... ........ . . g...... X.fsor.adyHo X................. ................... sss:: :: ::: : s::::: ::::: ::i::::::::i::::: ::::: ::sss:::s:: ::!::'::!::I::~:!::::1:I::::!:I:::::::: : ' - ' 's s~~~~~~~~~~~~~~... ......'.sss..... ::S:':::::::.::::...:: : :::.::::::::::: :;::::::::::::: ::::::: :::::::: :::::::::::::::::::s::::::::::::s::::::::::::d u .' ' s ... .......... ....... ...................... ....... :S::: :. {E v L~~~~~~~~~~~i s S O.: {, 2 Ot>: : V:::::' :':: ssss ....ss..ss.s.sss . ... ~~~~~~~~~~........................... ....... .. ...... ...... ... ... .... AtaicCy ~~~~~~~~~~~~~~~~~~~~~............. ............. 390 ~ ~~~~~~.... Cit ofi ........................... i::.:::sss:::s.:.:.:.:.:.:.:.:.: s::ss::.:i:::ss::-:: Neas Cape Mayijiilll~~ ����������������....�-........ ' . ...... ~~~~~~~~~~~~..ss.ssf:.:.:.:.:.:.:.:.:.:.:.:.:....................-. :.-..........Five.Fathom.Bank ~~~~~~~~~~~~~..................s ssss ......................Ofhre.llvr a s:.:.:.:I:I:ij:I:: l .........:. .::.:... ::::: .:: :................................ Es: s~ ~ ~ ~ ~~ ~~~~~~~~~~~~~~eer .,s . :.ss.s S...... :s.:::ll~iiiiilldlii :ss-:fliiilIiiiiiliii :s:::..,.:.. s::: ::::::s: s ,,,, s ,,~~~~~~~~~~~.,.....ss~~ss..... .......: ......................:.........,,. . s,. . . . . . . . . . ,B .,,::::-::i:::::::sss:S ::::- :s:ss :::::ss: : . BS::: ~ ~ ~ ~ ~ ~ ~ : ::::::: SS:: S SS :S:SS:: SSF- ;SS:.:i::3::::::::': :SSS :'.S:::i:i:i:i) Fig.6 Ne Yor andDelaareBayaramp ..... ....� �..........�� ......................�t; 9 ........ Sandy Hook� ::�::�::�: ............. .........................: iiiij~) iiitiiiii~iliiiili.................... ....................... .............ii :;:;:;i:;:;:;::::::;:;:::::........... . ... ..... ... ..................''' il~~nlaaaiaira..... ............ i% ................... . .... ...... .......... ...... . R.... ........... .......................... r anBa ........................... :::::ii:::::j........... Offshore Sandy Hookiii~ ................................................. .......................... .................... .. . .......................................... ................ ........................................iiiij Alanti Cit ......... ..... .. .......................................... ........ ........~~~~~~~~~~ii� ........ :. , - - - - - ....... . ... ........ .. ............eof npeMaylll ....... .... ... ......... ......................... iiiiiiiiiiiiiiii................................. ......... . ................~~i:~ii~ii~ri~~is~i .......... .. .... ............f ... ............................ ...... .. .........I....... X.. . ................,~, 8 ..................... (��:�:�:�:�................. . .. .. ...... IPI~~~QliS~~iiZ...... .............. ..... ~~~I1~FI~i~.......... ..... ........ 380 P ~~~~~~..................... ......................... ...... ............................ .............. .................. .............. Deep-draft vessels use established traffic lanes at the At- lantic entrance to Delaware Bay. The entrance is about 10 miles wide between Cape May on the northeast and Cape Henlopen on the southwest. The channel into Delaware Bay is broad and deep, and has an average current velocity of 1.8 knots. Delaware Bay is an expansion of the lower part of Delaware River. The Bay affords the only protected anchorage for deep-draft vessels between New York Bay and Chesapeake Bay. Delaware Bay is shallow along its northeast and southwest sides and there are ex- tensive shoal areas close to the main channel. The Bay has natural depths of 50 feet or more for a distance of five miles above the Capes; thence federal project depths of 40 feet to the upper end of Newbold Island, 110 miles above the Capes. In ordinary winters there is usually sufficient ice in Delaware Bay to be of some concern to navigation. The tidal currents keep the ice in motion. THE ENVIRONMENT The Appalachian Mountains, although some distance from the ocean, exert an important influence on the winter climatic pattern in the coastal area. They partly block the cold continental air from the interior, and this combines with the moderating effect of the ocean to produce a more equable climate than is found in con- tinental locations in the same latitude elsewhere. 60 The general surface wind pattern along the Atlantic coast is controlled largely by the position and intensity of the Bermuda high-pressure system. The characteristics and location of this extensive high vary considerably during the year. In the winter, it usually is centered far to the southeast. The major low-pressure storm systems, which develop over the interior, the Gulf of Mexico, and off the southeastern coast may sweep through the Middle Atlantic States. These extratropical cyclones usually travel between north and east-northeastward. Many are intense and accompanied by strong gusty winds and rain or snow. Highs from the interior usually follow-the passage of these Lows, producing a pattern of rapidly changing air masses and vari- able winter weather conditions. There are marked temperature fluctuations and an alternation of brief stormy periods with clear crisp days and relatively mild weather. In the spring the Bermuda High, although still centered far to the southeast, begins to affect the southeastern states. The Middle Atlantic area usually is located outside the high-pressure circula- tion, however, and is still subject to the passage of extratropical cyclones, frontal activity and changing air masses. Warm spells, sometimes with abundant rain, alternate with cool, dry weather. In the summer, the Bermuda High reaches its most northerly and westerly position, embracing the entire eastern seaboard within its circulation. The strength of this circulation is moderate but per- sistent, sufficiently so to hold back the eastward movement of the 61 continental low-pressure system. As a consequence, the daily weather along the coast may not change much for several weeks at a time; it is controlled by the southerly and southwesterly winds bringing moist, warm air from the Gulf. This weather is character- ized by frequent instability showers and thunderstorms, uniform warm temperatures and high humidity, and relatively low wind speeds. However, the summer months also include the beginning of the hurri- cane season. In autumn, the Bermuda High again shifts southward and eastward, leaving the Atlantic coast in a weak continental high-pressure area. This gradually gives way to the winter weather pattern, bringing increased frontal activity and more frequent passage of cyclones and anticyclones. Pressure The pressure pattern over the Delaware area changes cons ider- ably from summer to winter. However, the differences of mean annual pressure between the Delaware Bay area and offshore Delaware Bay area are negligible. Large short-term variations of pressure are occasionally experienced during tropical cyclones in the late summer and autumn, and during the movement of extratropical cyclones and anticyclones in the winter and spring. The day-to-day changes of pressure in summer are less marked. Extratropical Cyclones The frequent winter extratropical cyclones traversing the Delaware area produce frequent shifts from the prevailing wester- 62 lies and produce rapid changes in the weather. The cyclones may be of continental or marine character, with the latter (Nor'easters) usually being of greater severity from having passed over water. Strong winds, sometimes of hurricane force, accompany the storms. * ~~The northwesterly winds in the western half of the storm, having come directly from the interior of the cold continent, will often be very cold. Appendix B contains extratropical cyclone tracks and movement roses. The Machiasport narrative contains a detailed description of "Nor'easters." Tropical Cyclones Tropical cyclones occur almost entirely in six rather distinct regions of the world; one of these, the North Atlantic Region, in- cludes the Delaware area. Tropical cyclones are infrequent in com- parison with the extratropical cyclones, but they have a record of destruction far exceeding that of any other type of storm. The tropical storms are most frequently oceanic and, therefore, of greater fury. As a tropical cyclone moves out of the tropics to the Delaware latitudes, it normally loses energy slowly, expanding in area until it gradually dissipates or acquires the characteristics of extra- tropical cyclones. At any stage, a tropical cyclone loses energy at a much faster rate if it moves over land. As a general rule, tropical cyclones move with the prevailing winds of the area. 63 The frequency of occurrences of tropical cyclones for the Delaware areas (as they appear on the map'in Fig. 6) are noted in the table below: Total Number Average Number of Years 1886 - 1971 between Occurrences Tropical Cyclones 11 8 Hurricanes 3 30 Of the 11 tropical cyclones, three were hurricanes while in the vicinity of the Delaware area. Appendix A contains detailed information of the study area for tropical cyclones. A summary of tropical cyclones for the Delaware Bay area strike zone is presented in Figure 7. Winds Prevailing winds over both the Delaware Bay area and offshore Delaware Bay area are from northwest during the cooler months, November through March, and from a southerly direction May through September. April and October are the transition months of the seasonal wind systems and are quite variable. The average wind speeds during the warmer months are generally lower than during the cold seasons because of the absence of extratropical cyclones. The winds over the ocean area are stronger throughout the year than winds over the Bay area. However, the differences are smaller during the summer period. In the warmer season, a daily shift in wind direction occurs when the regions are not under the influence of cyclonic storms. 64 1 00� 95� 90 � 85� 80" 75� 700 650 500 50� 450 1) c M/hopr 45' Ne York 40� 40" CATEGORY MAXIMUM SUSTAINED WIND SPEED Cape Mayl TROPICAL CYCLONE GREATER THAN OR EQUAL TO 3-_4KNQIS HURRICANE GREATER THAN OR EQUAL TO 64.NMO15 INTENSE HURRICANE GREATER THAN OR EQUAL TO 19_-KNQIT 35� 35� 300"oesn . New OrleansC,: , 30 25" 250 100� 950 90� 85� 80� 75� 70� 650 AREA Delaware Bay PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 1% 85 1 HURRICANE 1% 85 1 INTENSE HURRICANE <1% Fig. 7 Tropical cyclone strike zone and probabilities for the Delaware Bay area. 65 During the warmer part of the day winds blow onshore, and during the cooler part, offshore. This land-sea breeze seldom penetrates more than a few miles inland. Gales (greater than or equal to 34 knots) are reported in about five percent of the observations over the ocean area during winter, and about half that number over the Bay area. Summer gales are rare, but may be encountered during tropical cyclones or local thunder- storms. Again, the frequency of occurrence decreases from ocean to Bay area. Extreme Winds As sufficient wind observations are unavailable for the Dela- ware area, both in time and space, the return values of maximum sustained winds, for the Bay area and the Offshore area, given in the table below, are based primarily on statistical estimates. DELAWARE BAY AREA Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 63 kts 70 kts 80 kts 92 kts OFFSHORE DELAWARE BAY AREA Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 71 kts 80 kts 92 kts 100 kts For example, on the average, there will be a maximum sustained wind speed of 63 knots in the Delaware Bay area once in every five years. 66 Waves The distribution of high waves is roughly the same as that for the windiest period for the Delaware area. Maxima for the Delaware Bay area are significantly less because of the combined effects of weaker winds and insufficient fetch. As with the winds, because there are insufficient observations for a climatological conclusion of significant wave heights, the table below primarily reflects statistical estimates. DELAWARE BAY AREA Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 11 ft 14 ft 17 ft 22 ft Extreme Wave Height 20 ft 25 ft 30 ft 35 ft OFFSHORE DELAWARE BAY AREA Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 37 ft 41 ft 47 ft 53 ft Extreme Wave Height 60 ft 70 ft 85 ft 95 ft Visibility Although generally good over the Delaware area, visibility at any time can be hampered by smoke, haze, fog, and precipitation. The frequency of occurrences for visibility less than five miles is greater throughout the year for the Bay area, while the annual range is quite small when compared to the Ocean area. Advection sea fog occasionally drifts onshore in the warmer months, burning off from the surface and usually lifting by after- noon. This process is reversed over the water area where fog usually dissipates from the top downward. Very shallow steam fog 67 FIVE FATHOM BANK ,I l r oII jI IlolI I I - .111X oI#t7AIIoI I - 1i0 - CASIONS DOWING THE YA -- 132 - CASIONS DWING tHE BR - - ERSITC 5OF WHAV WRABYE 0SE- - BO9 12H N WAHO P ERS O - 2 CI2220D 0I2 HEI2 T I0OW 0-- I12 T0 2 3000 2024G0. -- 5 .0 _ . ... -: ' _ _ t _:o- 2n E :� *. t so 2 0- ' -, 0 I, I , I : i ', m'Y' :.~kS -_ [ ....|I I I I I ,- oEET A.. ASE di w 1.0 I C0 Hlo 2N DRo 111 EN SEA AY o IASa 1 . CASIONS DRN 'HE SEA- W N 24 OCCASIONS 1150% X 16), AON WNons WUT DE. ON 24 OC PERSISTENCE FAVORABLE SEAS N < 6, 9, 12 FT.) PERSISTENCE or UNFAVORABLE SEAS (2 6, 9, 12 FT.) WINTER (JANUARY, FEBRUARY, MARCH) LEGEND AND EXAMPLES 150�2 2 1 1 Iso I Io140 6552 0ESERVATIONS WAV S ECEA SED IN HEIGHT ELOW 1.2 WAES ECREASED IN HEIGHT OW 16 AERAGE NUMBER O OC WAVES ROSE TO 9 FEET OR HIGHER 16 AVERAGE NUMBER OF OC. 190 4 9 FEET AND LASTED 6 TO >300 HOURS CASIONS DURING THE SEA. 130 - 4 AND LASTED 6 TO >300 HOURS CASIONS DURING THE SEA- - _ ON 24 OCCASIONS [150% X 16)' SON WHEN WAVES DE. - ON 24 OCCASIONS 1150% X 16T'' SON WHEN WAES ROSE 420 DURING THE SEASON. TON 6E OCCAR SS HIGHER - 120 ~ DURING THE SEASON. CREASED IN HEIGHT BELOW ON _' I E. T 6 5FEET. HIGHER . i I 410 - WAVES DECREASED IN HEIGHT BELOW 110- 6 FEET AND LASTED 6 TO 144 HOURS WAVES OSE TO I FEET HER AND LASTED 6 TO )300 HOURS 100 ON I2 OCCASIONS (100% X 16) 1TS ON 16 OCCASIONS 100% X 16} THE SEASONDURING THE SEASON. - J -- DURING THE SEASON. 970 z - 1H - WAVES DECREASED IN HEIGHT B ELOW - - \ WAVES ROS E TO 9 FEET OR HIG HER *0 : , --- - - FEET AND LASTED 451 T>3D00 OURS AND LASTED 47 TO >3 00 HOURSS - _ _ON H OCCASIONS 50% X 161DURING 1 ON OCCASIONS (50% TH SEASON. DURING THE SEASON. THE SEASON. _I I _- WAVES D ECREASED IN HEI GHT BELO W WAVESIROSE TO 9 FEET OR HIGHER 40 -12a.zG FEET AND LASTED 128 TO >300HURS HOUS ON OCCASIONS 125% 1 OCCASIONS 5% 16 DURING - FEET, THERE ARE TE C E W12E ' 1 6 H HIGHERT 30 DURING THE S EASON. G THE SEASON. = ..... 1101_ Fig 822 P~~G E Enc- 4f 20 o.. s i d g, at Fv Fathom.. -n 0 4 20 0 IO 20 20 00 200 224ET 2N2 22 30S2 2 20 12 06 12 200 220 0 2 2 00 DURATION (HOUR') DURATION (HOR..) MA AR, THE- INTRRETATION OF THE GRAHICS REMAINS THE SAME. A E HEIGHTS (FEET) I-. I. . .. -OR 6 2 - � Fig. 8 Persistence of waves of specified heights at Five Fathom Bank. 68 FIVE FATHOM BANK Iso 'R EA . SIS , '1 I I' I TO 2 I R ' S 0),, -,, , , ,,,,, Ila z~dosStarao^S Iuo a> weAuaOs _ _ 1 ' 1'TV N1I ' I - _G I O� K. 32t O-SEION$ mC T Y _ 1V - - 3;* CeVAItONS DU--^C _SON HEN W A*VES DE _- SON WHEN WAVES R OSY - ia0 <cASEc0 i~ HE~O. IEOW -- 12o t FIo cf .o~~~~~~~~~~~~ - ier 110 :10 _ ,_ ' 6~~~~~~~~~~~ ITS so-- -.. 10 ., " " - ,o - ! 2a 1 _ 0 - _ bl... ........ ll 60- - 5 '" -, 1 ,, ~11~1 1,11,1, ,I, ,I, , GO I0 4G E0 a I 0l 12o I,0 lX o0 221 o 2O 2do 200 001 0 'o 0 0 BO l R OR20 1.I l I 2l X 2~O 2'0 t 20 IO oUsnoH IHOYU) DJ-UA pwOUlS) PERSISTENCE OF FAVORABLE SEAS (< 6. 9. 12 FT.) PERSISTENCE OF UNFAVORABLE SEAS j1 6. C. 12 FT. SPRING (APRIL, MAY, JUNE) isa , o , , ,, ,,, ,, 1, 1 IIso, ~ ,, ' ~ ,1' 'lll''- so ~ ~ ~ ~ ~ ~ ~~~0 0020 ObEVIObOS _0 - ^ zSCON 12 VA ONRS ROE_ IS -RCASIONS DURING m1 20 0 -10 - TSON EE DURNG ITO _2- STEET io C--*YD H wlc"T aro _ wo 1 ol a *m " _1 ION K.~~~~~~~~~~~~~~~~ ,- \ ' -. ., t ol . 60*, ' -- � ,UESTNOI (0000) 602020 20060S) PERSISTENCE OF FAVORAILE SEAS (< 6, 9, 12 FT.) PERSISTENCE OF UNFAVORABLE SEAS {K 6. 9. 12 FTI. SUMMER (JULY, AUGUST, SEPTEMBER) -o 1 GAOERAGE NUAIER Of 0C- 1c _ARAGE OASD ER OT 00- - 12o - 001002DNG E O TOE _24 - 120 -- 402.002 EURIN me 5 - - SoN WORN WAVES ST - 5ON wnEN W02ES 202 -_ o20 C"SEED ES HERO. RIoW -_ 100 TO 2 FERRIT SE -0E. _ --lO - - 11 ~oE _6 1o10_ ,FC ro _ F- ~.". ...o , o ' _ |~~~~~~~~~~~~~~~~~~~~~ a~ , F�, ,- s~~~~ ~ ~ ~~~~~o-~"" ., O. . . . _ DJUAIO CHOUnI] DWUSAONa (HOUS PERSISIENCE OF FAVORASLE SEAS (< . 9, 12 FT,) PERSISTENCE OF UNFAVORABLE SEAS ( 6., 9, 12 FT.) AUTUMN (OCTOBER, NOVEMBER, DECEMBER) Fig. 8 (Cont.) Presistence of waves of specified heights at Five Fathom Bank. 69 is sometimes experienced in the winter. This fog type, which occurs only in very cold weather when the air is much colder than the water, may hide the hull of a ship while leaving the masts and upper rigging plainly visible. Fog is more likely to form with light to moderate winds. The greatest frequency of fog occurrence coincides with the period of weakest winds. Fogs usually come in with easterly winds and are cleared away by westerly and northerly winds. In the late fall, dense fogs are liable to occur and may last through the forenoons for two or three days in succession. Autumn fogs nearly always clear away before noon. Fog rarely forms or persists with gale force winds. The number of observations reporting fog over the Delaware Bay area is approximately twice that reported over the Ocean area. Temperature Temperatures are generally moderate along the Middle Atlantic coast. The Ocean area east of the Delaware Bay area has air tem- peratures with a slightly higher annual mean, a slightly smaller annual range of the monthly mean, and A significantly smaller annual range of the extreme Air temperatures than the Bay area itself. Such differences occur because of the decrease in land effect seaward and because the sea temperatures are typically warmer than air temperatures during the cooler months and cooler than air temperatures during the warmer months. Over a land surface, the air warms and cools readily, but over water it does so more slowly. Land surfaces 70 absorb heat in only a thin surface layer and give it up freely, while water absorbs heat to substantial depths and retains it longer. The lowest and the highest mean monthly air temperatures for the Bay area occur in January and July, respectively. There is a month delay over the Ocean area; again, because of the oceanic effect. The daily air temperature range near shore averages from 100 to 20'F throughout the year, and is generally much less over the water, decreasing with distance from shore. Readings rarely exceed 100'F and the 90'F level is reached on only one-third to one-half of the days during summer. Freezing temperatures are probable on one-half or more of the days from November through March. Below- zero readings have been recorded during December, January, and Feb- ruary at most of the nearby coastal stations. Precipitation Precipitation over the Delaware area is moderately heavy and well distributed, but having a general decrease seaward throughout the year. The maxima occur in winter, while the minima occur in summer. Summer thunderstorms are more frequent in the coastal area in the afternoon; at-night they are more frequent over open water. Thunderstorm rainfall is less intense over the ocean, but can severely restrict visibility. July is the month having the greatest frequency of thunderstorms for the general area. 71 Snow may be expected from November through March, maximum fall being in January and February. On rare occasions, freezing rain, or glaze, is encountered; if prolonged, it can cause damage to rigging. Snow at sea can be a severe restriction to visibility. Cloudiness At sea in winter, overcast conditions are recorded in about 30 percent of the observations, while clear conditions (2/8 or less) are recorded in about 36 percent. In summer, some 20 percent of observations show overcast and about 40 percent clear skies. Over the Bay area, overcast conditions occur with greater frequency throughout the year, while clear skies occur with slightly less frequency. The least cloudiness for the general area occurs when the air is dominated by the Bermuda High in late summer and early autumn, and the greatest cloudiness during the frequent winter cyclones. The annual mean cloud cover over the sea is about 4/8, with the Bay area being slightly higher. Relative Humidity Throughout the year the relative humidity is high, with the annual mean for the Ocean area being greater than the Delaware Bay area. The summer months will average higher for both areas because of the more persistent southerly, weaker winds. Humidities for the coastal area usually increase with onshore winds and de- crease with offshore winds. 72 Tides and Currents - Offshore Delaware Bay On the outer coast of Delaware, the spring range at Rehoboth Beach is 4.7 feet. Maximum flood and ebb at the Delaware Bay en- trance are 1.8 and 1.9 knots, respectively. More detailed informa- tion is presented in the following summaries: Mean Tidal Spring Tidal Mean Tide Location Range (feet) Range (feet) Level (feet) Five Fathom Bank 38�51'N 74�38'W 4.1 4.9 2.0 Cape May Mun. Pier 38�56'N 74�55'W 4.3 5.2 2.1 Rehoboth Beach 38�43'N 75�05'W 3.9 4.7 1.9 MAXIMUM CURRENTS LOCATION FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) Delaware Bay Entrance 38�48'N 75�01'W 305 1.8 140 1.9 2 miles NE of Cape Henlopen 38�49'N 75�03'W 315 2.0 145 2.3 The highest storm surges off Delaware Bay are probably the re- sult of hurricane passages, though little data are available for confirmation. Extratropical cyclones can also cause considerable surges. The highest surge to be expected in the offshore Delaware Bay area is estimated to be about six feet above mean high water. 73 Tides and Currents - Delaware Bay Inside Delaware Bay, spring tidal ranges are about five feet and maximum current speeds about 2.5 knots. Detailed data appear below. Mean Tidal Spring Tidal Mean Tide Location Range (feet) Range (feet) Level (feet) Cape Henlopen 38�48'N 75�05'W 4.1 4.9 2.0 Breakwater Harbor 38�47'N 75�05'W 4.1 4.9 2.1 MAXIMUM CURRENTS Location FLOOD EBB Dir. Speed Dir. Speed (deg) (kts) (deg) (kts) Delaware Bay Entrance 38048'N 75�01'W 305 1.8 140 1.9 0.3 mile N. of Cape Henlopen 38*48'N 75�05'W 300 2.0 125 2.3 / Though the offshore islands serve to protect Delaware Bay from the ranges of extremely large surges, levels of four feet above mean high water have been achieved by the passage of extratropical cyclones. Tropical cyclones can also be expected to produce signi- ficant surges. Strong easterly and southeasterly winds sometimes cause high tide in the Delaware Bay and the Delaware River, resulting in the flooding of lowlands and damage to bay front and river front pro- perties. 74 STATION: DOVER, DELAWARE POSITION: 39.2N 75.5W ELEVATION: 25 FEET Means: 1931-1960; Extremes: Oct 1891-Dec 1896, IaIS AD EXTREMES FOR PERIOD Jan-Dec 1898, Jun 1906-May 1916, Aug 1919-Dec 1965 Temperature (�F) * Precipitation Totals (Inches) Mean number of days Temperaures Means Extcemes -Sno, Mle er M .~ Max. Min. I~~~~ ~~~~~~~~~~~~ a 55 CD IS 1'- cr. 41iWSLO, ii~~~8a.~~~~ r p: r 1: ~~~~~~o ~aqo (a) 30 30 30 61 61 30 30 61 30 61 61 30 30 30 30 30 Jan. 44.8 27.8 36.4 76 1950 -7 1935 887 3.70 2.68 1936 4.3 20.5 1940 15.0 1928 7 0 3 22 * Jan. Feb. 46.0 27.5 36.8 80 1930 -11 1934 790 3.03 2.30 1936 4.7 22.0 1934 10.0 1936 6 0 3 20 * Feb. Mar. 53.6 33.8 43.7 88 1921 '7 1934+ 660 4.12 3.00 1912 2.8 23.0 1914 8.5 1960+ 8 0 1 15 0 Mar. Apr. 65.1 43.1 54.1 95 1896 14 1923 327 3.42 3.35 1928 T 15.0 1915 15.0 1915 7 * 0 2 0 Apr. May 75.6 53.3 64.4 98 1914 32 1947 84 4.15 5.40 1948 0 0 0 0 0 8 1 0 0 0 May June 83.7 62.3 72.9 101 1914 41 1938 6 3.46 3.96 1943 0 0 0 0 0 6 7 0 0 0 June July 87.4 66.9 77.1 104 1936+ 45 1963 0 4.67 4.52 1938 0 0 0 0 0 6 11 0 0 0 July Aug. 85.4 65.4 75.4 100 1953+ 47 1925 0 5.73 7.42 1919 0 0 0 0 0 7 8 0 0 0 Aug. Sept. 79.8 58.9 69.4 99 1953 33 1947 27 3.81 6.33 1960 0 0 0 0 0 5 3 0 0 0 Sept. Oct. 69.3 48.1 58.7 95 1941 25 1909 220 3.27 3.30 1910 T 3.0 1940+ 3.0 1940+ 5 a 0 1 0 Oct. Nov. 57.9 37.9 47.9 85 1950 11 1938 513 3.67 3.35 1950 0.7 10.0 1953 7.0 1953 6 0 * 10 0 Nov. Dec. 46.7 29.1 37.9 74 1964 -3 1942 840 3.11 2.40 1909 3.0 25.0 1909 24.0 1909 6 0 3 20 * Dec. Year 66.3 46.2 56.2 104 1936+ -11 1934 4354 46.14 7.42 1919 15.5 25.0 1909 24.0 1909 77 31 10 90 * Yea (a) Average length of record, years. + Also on earlier dates, months, or years. T Trace, an amount too small to measure. * Less than one hall. a* Base 65�F Table 9 Land station climatological data summary for DOVER, DELAWARE. 75 STATION: WILMINGTON, DELAWARE POSITION: 39.7N 75.6W ELEVATION: 74 FEET NORMALS, MEANS, AND EXTREMES Temperature ~~~~~~~~~~~~~~~~~~~~~~~~~~~preipitation Relative Wind & nMean number of days humidity Normal Extremes a Sunrise Teeperatoirs~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..iTep,.. E~~~~t..e. L ~~~~~~~~~~Snow, IC. pellets -- -. Enses mite a.. n sal, a 3 sunset ii Plan. Olin.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~a o 0i0 m e . ~~~~~~~~~~~~~~~~ ~ ~~~~~~~~01 07 1319 u0 S 0, - ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~,, 02 oren a .00.0Ca~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Ac., in0, my I -~~~~~~~~~~~~~~~~~~~~~~~~~~ u u sn-na~~~~~~~~~~~~~E 7;~ ~ ~ ~ ~ ~ ~~~~~0. E-a >0udu'0 0' 9 0,P om . '22 s' 5 o'2 .~~~,.. -- .3..- ,. Oj3 m~~~3 ...4 0'e..a-5 90. 0 ~ v 2 23 33 23 23 23 23 23 23 23 23 2323 22 1622 22 23 23 23 232323 2323 2323 233 () (6) (h) (h) (6) (6) J41.3 Z:23.3 33.4 73 90 19597 90 3.4 3.3 1949 0.39 1985 1.61 1968 6.0 17.2 1966 11. 1966 74 78616098 46 29 1937 6. 8 7 1 11 2 * 4 0 7 6 * F 42. "4 1253. 338 74 1954 -412961 87 293 4.90 1966 1.32 1968 2.29 1966 6.0 15.7 1967 9.9 1967 7 73 9671. NW 4 29 96 64 7 7 t 9 2* 4 0 4 3 * 9 0. 2.3 41.3 86 1948 9 196 733 402 5.72 1933 0.81 196 6 2.73 19390 4.3 203.31938 19.6 1958 7373 54 64 111 94 3 16 2933 6.3 8 8 1 12 1 13 0 1 17 3 A 2. 416 9. 8910 22196 38 3.3 397 1964 1.12 1963 2.36 1961 0.1 I.1 195 1 11989 7 4 3 621. 44 43 9163 63 7 8 1 1 *2 3 0 0 3 5 818 1. 1. 99 1932 44 196 6 4.07 6.34 93 04 198 267 193 . 0.0 5 0.0 83 783 62 8. 45 27 1960 3.+ 1 1 '55 86.2 65.38 76.30 C102 19636, 30 1932 0 4. 23 7.51 1958 0.16 1953 6.24 1952 0.0 0.0 0.0 84 81 84 67 7.6 NW 48 27 1963 6.1 7 12 12 9 0 6 2 8 0 0 3 6 84.2 64. 74. 10 193 46 19 63 0 3.912.09 1955 1.17 1968 4:.30 91933 0.00 0.0 0.0 86 64 36 71 7. 3 S 40 OZ 1960+ 38 9 190 12 9 0 6 3 3 0 0 3 O 77.9 57.3 67.6 100 1953 37 963+ 31 3.93 .316 .217 .216 . . . 58 47 . 40 07 1956 3. 10 9 11 7 0 2 t 2 0 0 0 0 67.3 45. 66 91 11951 24 1969 270 2.91 31 16 0.21 1963 3.88 1966 T 0.3 1962 0. 3 19162 813 84 33 : 71 8. 41 NW 38 20 19354 3. I12 7 132 7 0 1 4 * a 2 0 N 31 33. 4'5.4 832 119650 1 41953 388 3.33 73 21931 0.94 1965 3.83 1936 1.3 I11.9 1 193 11. 193 79 813 0 91N 6 6 218 6. 8 3 4 0 * 11 3D 3 43.3 26.7 35. 1 72 1966 3 962 927 3.03 7. 90 1969 03.19 1938 2.22. 19 69 4.7 21.3 1966 12.4 1966 76 77 60 70 9.3 434 44 2 192 63 8 a 13 0 1* 4 0 3 2 Y I ~ ~~~~JUL. PE"'1.9AUG 4 0. 1 JUL. JUL. DEC. MAR. OCT. YR 63.8 44.4 94.1 102 1966 -4 1961. 4933 44.56120 1933 01 1953 6.24 1952 22.4 21.5 1966 15.6 1950 79 79 35 68 9.0 NW 38 20 1934 6.1 98 107 160 113 6 SI 40 19 16, 104 * - Means and emtrmeu. above are from existing and comparable exposuree. dAtnual extremtes have been excee.ded at other uites in the Ilocality as follocro; Higheut temperature 107 its Asuguut 1918; lowest temperature -15 in February 1934; toaxiresn monthly precipitation 14.91 ins August 1911; moinrtxn monthly precipitation 0.06 in October 1924; main.iotun pr~enipitationx inu 24 hours 6.53 in August 1945; mamious mothly onowlall 27 .0 in January 1935; maoinso unovfall in 24 hours 22.0 in December 1909. fa) Leegrh no recod, pear h.. bsd en J---"r dora. L1i1k0. otews Ixdicare di..-,-atoat. uoiuaud to ths boicIts are r.omperatur In deg,... P.; &Figure Isoread cf lerrors ins drecton column indIc-e dirietIon to..e. of deMree from Inre North; re mmo a b ormreo fewer years if praoipirtiuo.% toIiadle -eafaL, is toh.id mo.nmeto mInteI. per knour; and reaeumdity iLe., 09 - Eos, iS- Sooth, 27 -Went, 26 -North, and 00 -Coin.' Re.xalin wind L. the st-eor u or ibere hare 'Le brasi bercri palerti Near1ing dEl-edynoeo ddo sooob ete depa"ire no overag daily nepera- sled directions and speeds divided by the number of ohorvato~no. If figuons sppr L. the dirotino fbI Citmaratasicat sadartdI earat fii-00. _ un ro 5 P. Cantin dege dyoaII.ar the uso oiiedproe faeaediy oim ne Fsetmt"se co .opendIog speeds Iarr - fairi ho d 1-mIc vau... Lea. thas seabai. remper~ase from 63' P. Stem W.. Ictaded x snowfall roai betsx IrJl 94i Th. sp-n 1' Ata on arie dares, mioha, or year. " I.. -paletters inclde s=~ go of I..c.efeteen and poritelso consisris of samo pellets e-axd T Tran, so sm-r ian a.-al to me.ure in thin taper of tee. iteovy rol l reue ixihilfty to 1/4 mnim or l.es. Bela. rer .erperaru.. .cprecdd by amino. aige Tire ptevaitig direxios r wind in the N-rmsa Sky cove is noprerend tea range. f 0 foe co otouda or ohanc phecomocon no 10 for comPlnse .ky Meaea, aMd bmrme rob I.. 8rmsoda brough cover. Th. number of clear day. is haned us anrge otaudiseas 0-3, panty cioudy days 4-7. and 1963. cnoudy days 8-1 tents. * 781 at Alskrm s~taIoss Sotar radiation dat are the over.gexof dIrtr ad diffase redirin san baricoorlat ufet The tasgigy deeree nnegam V..tarte pee square coxtlmeetr. Table I10 Land station climiatological data summary for WILMINGTON, DELAWARE. STATION: ATLANTIC CITY, NEW JRESEY POSITION: 39.SN 74.6W ELEVATION: 64 FEET NORMALS, MEANS, AND EXTREMES Temperature Fren~~~~~~~~~~~~~~~~~~~~.ipitaton . ReaieWind&nMenumrofdy hmdity M. .bffy L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ii ~~~~~~~~~~~~~~~~~~~~~~~~,~~~~~~~~~~~~~~~~~~~~~~a 'R 8c cC. oP eg - o e n on e 5, u.2 nnn 19 (h) (h) 6 6 b)27 27 27 26 26 26 6 6 6 6 12 2 1 111 10 12 12 12 12 27 26 12 12 6 6 6 6 4? 459 26.6 54:.8 78 1967 -5 19635 936 3.56 7.71 1948 0.26 11955 2:.86 1944 5.2 15.9 1961 14.411964 72 77 58 70 12.3 69NW 37 29 1963 54 5. 10 7 16 11I1 3 0 9 26 1 F 43.3 26.134.7 69 1965 -71967 848 3.13 5.98 1958 1.46 1946 2.59 1966 5.2S 3521967 13.1 1967 73 76 56 66 12.4 8 43 27 1960 20 6.94 7 6 15 1102 *4 0 6 23 1 M 49.7 32. 44. 51 1988 71967 741 5.91 6.80 1953 5.62 1943 2.27 196 3.6 1. 199 13 1969. 767 46 2466 4 016-. WNW 6.0 94 12 1 a 0I 2 A 60.5 41. 510 94 1969 12 199 420 3.1 79 92 12 92 33 92 0 3 32 1965 321965 78 76 166 12. 2 460 191 5 6.4 7 9 14 1 *2 4 * 0 7 0 M4 71.0 51.5 61.3 99 1969 25 1966 133 2.51 11.51 1948 0.40 1957 4.15 195 9 0.0 0.05.0 (I81 75 52 66 10.8 � 32 22 1966 56 6'.2 7 12 I2 1la0 4 4 1 0 1 0 ..J 79.2 60.7 70. 106 1969 37 1967 15 2.83 6 .3 I970 0.10 1954 2.91 1952 0.0 0.0 0.0 58a 82 56 72 9.8 2 37 29 1964+ 61 51.9 a 11 11 9 0 5 4 5 5 0 0 J 83.8 66.3 75.1 104 19666 4(6 1965 0 3 372 13.09 1959 1.30 1937 6.46 1959 0.0 0.0 0 00 89 86 .59 74 9.2 S 37 26 11970. 57 6.4 7 9 15 9 0 A 5 5 0 0 0 A 822 65.13 7.7 97 1965 40 1965 0 4.90 11.95 1967 0.24 1943 6.40 1966 0.0 0.0 0.0 90 56S5675 9.0 5 32 32 1Q63 62 6.0 8 I0 13 9 0 5 35 a a 0 2 76 .0 58.4 67.2 93 197 0+ 32 0969+ 39 3.31 6.27 1966 0.41 1970 3.98 1954 a.0 0.0 0.0 a 9 a6 5477 9.7 ENS 60 32 19 60 61 5.4 11 8 I1 -7 0 1 3 2 o * 0 066.5 47.8 57.2 87 19617 23 1969 2.5132.20 7.5a 1943 0.15 1965 2.98. 1958 7 7T92 962+ 56 86 54 76 101 N 41 29 1961 6551 12 8 It 7 0 1 5 0 5 4 5 N 55. 37.9 46.7 76 19 65 311964 549 3.66 8.65 144 0.72 1946 3.95 1955 .5 7.8 119667 7.51967 51 84 57 75 11.5 W 40 27 1960531 a. 15 9 + 1 3 0 * 1 O 45.1 28.1 36.6 72 196 019 68 Sea 3.22 7.33 1969 0.62 1955 2.75 1951 2.8 8.6 1960 7.5 1960 76 79 59 72 11.6 WNW 55 36 1960 46 6.2 9 a 14 9 1 *4 0 3 2ad* JUN.1 JA6N. JUL 1JN. JUL. OB JA6N. 3 SE6P. YR 62.0 45.2 54.1 106 1969 -8 196 4812 42.36 121.09 199 0.1015 6.46 1959 17.7 35.2 1967 14.4 194 2 at 55 71 10.9 5 60 3 9055 6.0 103 105 157 112 2 26 46 19 19 118 2 0 For period November 1964 through the current year. M ...no and eat~remeo above are from emiating and nomParable ompaoures. Annual extremes have bee .....eded at other sit.. in the locality a. followor tourent temaperature-9 donFbruary 1934; maximum monthly precipitation 14.87 in August 1882; minier monthly precipitation .01 in Sep tember 1941; maximum precipitatio-o 24 hourn 9.21 jot October 1903; mamiom nfall in 24 hours 15.0 in February 1902. Iat Leirgnh t rennd, yeoru, honed on Jano.ry data. Unlu oterle eivrd dmenuenl ..un..tie oed tn thi. ho1te over temporatoe In degrero F.; Ft lotne teuted or leter In dlceoslon voum ldbe dl-ect on In. tuun deu.ee Irow -en N-eh; termoehoa he a oen Cmeyaoi precplraitne incloding unetal, to techeor mInd J.emn in mle per hoa; nod relatIve homlty i.e. 25 Lor t-voh 7 et 6-Nrh e S-Cl.Rulin 9dt h eienm chur have been breahe In the recod. Is Pecoent. H.eutte depuu. day ttll are the tome o neaIve deretre oraeaealepera- wted d rnI.Ie en.d nycede dtntded by th. nmber or u-hUerotn. If tiocen appea te the drei-It. (h) Clmanngeladanrd normal 11931-1960t. I _ re Ieem 65' F. Cooing degree day tWialu are th "o etive depetre Itveag daily neaead-rFnt mile~ t h. v-epond1eg upeede are tan.eat.o.eervd 1-mInoe as ee " ae non halt. epame te am-- 65' F. Stee ... Incloded Ineedl iil enlnthJl '1540B..Tghe Ir + Al.. In eartin dates, muntha, on yearn. leplet Inluaden noid goatee or i.. teeei and p."Iclvln c-nuetg ut ne pealI ..... eaed T Trace. , an ama in mOi eaae-atlelyro~e Hea-y ftu redanee vieilvlty to 1/4 mile or Ieo.7.B don1.. Nra.a Airpr Stato n ete ueuArotSation records. Th preattleg dorent.lun te mInd In she N-etel, Ik Ine to eo7eee le.ao t0 o nvtdseuhcrgyenmatottrvpeisy Me. o, aed ,oree tal to Irom renode theuah nee.The nabe t clea dayo In heaed ne average o.leoins 0-3, parily cloudy dayn 4-7 n $ Beginning with August 1943. 1903. cloudy doyo 5- 12 tenthe. *; 7 0 Mts Aleelas utalies. snlr rdiatinedatieoethae- averonu~evised dlrtte radiatson nTaheentlrav. Thelagley Table I11 Land station climatological data summary for ATLANTIC CITY, NEW JERSEY. ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Delaware Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 2 2 2 2 2 2 1 1 1 2 2 3 2 Mean 11.1 11.2 11.3 10.4 9.0 8.3 7.9 7.8 8.5 9.2 10.2 10.3 9.6 99% < 37 35 37 32 25 24 22 22 24 33 36 36 30 Maximum observed (1871 - 1971) Winds near 90 knots have probably occurred over Delaware Bay >34 Knots (% freq.) 2.7 2.5 1.8 0.8 0.2 0.1 0�2 0.3 0.5 1.0 1.4 1.8 1.1 >41 Knots (% freq.) 0.7 0.7 0.5 0.3 0.1 0.1 0.1 0.1 0.1 0.2 0.4 0.5 0.3 Prevailing direction NW NW NW NW SW SW SW SW S N NW W W WAVES (FEET) 01%S 0 0 0 0 0 0 0 0 0 0 0 0 0 00 Mean 3 3 3 2 2 2 1 1 2 3 3 3 2 99% : 11 10 10 9 9 8 7 6 8 9 10 10 9 12 Feet (% freq.) 1.0 + + + + 0.0 0.0 + + + + + 0.1 20 Feet (% freq.) 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + 0.0 0.0 0.0 + VISIBILITY (% FREQ.) Visibility <j N. mile 2.0 2.1 1.9 2.6 3.0 2.7 1.0 0.7 0.8 1.2 1.5 1.9 1.8 Visibility <1 N. mile 3.8 3.9 3.3 3.7 4.1 3.6 1.6 1.4 1.5 2.3 2.4 3.2 2.9 Visibility <2 N. miles 6.7 6.8 5.9 5.9 5.9 5.5 3.1 3.3 3.6 4.2 4.5 6.0 5.6 Visibility <5 N. miles 17.3 18.0 16.1 15.2 14.9 17.7 14.5 16.9 15.5 14.4 14.8 17.4 16.1 Visibility <10 N. miles 48.3 49.2 46.4 49.7 48.8 56.8 55.4 57.1 50.4 44.1 45.3 47.5 50.0 + - less than 0.05% Table. 12 Environmental data summary; Delaware Bay area. * 4 JT~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~1 ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Delaware Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 7.4 11.2 11.1 12.4 13.0 13.1 9.7 10.3 10.8 10.3 9.2 10.6 11.1 Mean number of hours operation of fog signals * 57 69 53 35 32 25 17 18 16 22 31 53 428 Maximum number of hours operation of fog signals for any year (annual only)* 840 WEATHER & CLOUDS (% FREQ.) Precipitation 11.3 11.1 11.0 9.1 7.3 5.6 4.8 5.3 6.3 6.4 8.5 10.0 8.1 Freezing precipitation 0.5 0.2 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.1 0.1 Frozen precipitation 3.4 2.8 1.9 0.3 0.0 + 0.0 0.0 0.0 0.0 0.4 2.0 0.9 Thunder & lightning 0.2 0.1 0.2 0.5 1.2 1.3 1.8 1.6 0.7 0.2 0.3 0.1 0.7 Sky 52/8 34.4 35.2 39.2 36.8 36.2 37.9 37.1 38.0 43.2 46.1 38.5 34.5 38.2 Sky overcast (8/8) 38.7 37.6 34.1 33.4 30.8 25.1 23.2 23.8 25.1 25.3 30.1 35.3 30.1 Sky obscured 5.1 6.6 8.2 9.6 12.4 11.4 4.7 3.1 2.5 2.2 2.1 2.7 6.0 Low cloud overcast 26.0 23.9 19.7 17.5 16.1 12.5 10.5 11.9 13.3 13.7 17.3 21.3 17.0 Mean cloud cover (eighths) 4.9 5.0 4.8 4.8 4.8 4.5 4.6 4.5 4.2 3.9 4.7 4.9 4.6 AIR TEMPERATURE (OF) Minimum -8 -7 7 12 25 37 46 40 32 23 11 0 -8 01% S 16 17 25 30 46 55 65 63 53 41 30 19 39 Mean 36.0 36.4 51.4 51.6 61.1 70.0 75.5 74.2 68.2 58.3 48.2 38.2 56.1 99% S 53 54 73 75 78 87 90 88 87 72 61 53 73 Maximum 78 76 87 89 99 106 104 101 100 91 85 75 106 5 32 �F (% freq.) 60.5 68.9 30.6 8.4 + 0.0 0.0 0.0 0.1 0.2 21.9 57.0 20.6 > 85 �F (% freq.) 0.0 0.0 0.2 0.3 0.7 19.8 28.0 20.3 10.0 0.3 + 0.0 6.6 * Mean of Miah Maull, Ship John and Delaware Bay Shoals fog signals + = less than 0.05% Table 12 Continued. ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Delaware Bay ENVIRONMENTAL FACTORS JAN FEE MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 72 71 71 71 73 76 77 77 77 76 74 73 74 SEA TEMPERATURE (�F) Minimum 28 28 27 33 40 41 54 57 56 46 38 28 27 01% S 28 29 33 39 42 53 63 65 58 51 44 34 45 Mean 41.2 39.8 42.5 48.6 56.7 65.8 72i'0 73.4 71.0 62.9 54.2 45.5 56.1 99% S 57 57 60 70 72 78 82 82 80 74 65 58 70 Maximum 80 78 76 80 84 88 90 88 90 84 82 80 90 SALINITY (%0) OD Minimum 20.6 21.6 21.6 20.6 20.8 20.0 25.5 22.2 25.4 23.0 22.6 22.4 20.0 O Mean 29.7 29.8 29.5 29.2 29.6 30.0 30.8 30.8 30.7 30.7 30.5 30.0 30.1 Maximum 34.5 34.1 33.6 34.2 34.6 35.0 34.6 34.1 34.1 34.0 34.1 33.6 35.0 DENSITY (p) Mean (at)* 22.0 22.1 21.9 21.7 22.1 22.4 22.9 22.8 22.7 22.8 22.7 22.3 22.4 SEA-LEVEL PRESSURE (mb) Minimum 977 972 971 981 991 992 977 976 985 993 979 979 971 01% < 993 988 992 994 1000 1001 1002 1002 1001 998 994 995 997 Mean 1019 1018 1016 1015 1016 1015 1016 1016 1019 1018 1018 1019 1017 99% S 1042 1041 1038 1035 1034 1032 1029 1030 1036 1034 1039 1039 1036 Maximum 1045 1044 1042 1040 1037 1038 1031 v 1041 1043 1040 1040 1043 1045 *at - (p -1) X 103; p- gm cm-3 Table 12 Continued. ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Offshore Delaware Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 3 3 3 3 2 2 2 3 2 3 3 4 3 Mean 15.7 14.6 14.0 12.1 10.6 10.0 9.9 10.3 11.6 13.5 14.6 15.0 12.6 99% 5 45 44 40 38 31 30 30 31 32 38 43 44 37 Maximum observed (1871 - 1971) Winds in excess of 100 knots have been recorded in Hurricanes and Northeasters. >34 Knots (% freq.) 4.6 3.0 3.2 1.3 0.5 0.2 0.4 0.6 0.6 2.2 2.3 2.9 1.8 >41 Knots (% freq.) 1.1 1.1 1.0 0.1 0.1 0.1 0.2 0.3 0.1 0.8 1.1 1.2 0.6 Prevailing direction NW NW NW S S S S S NE N NW NW SW WAVES (FEET) 01%-6 0 0 0 1 0 0 0 0 0 0 1 0 <~ Mean 4 4 4 3 3 3 3 3 3 4 4 4 4 O0 99% _ 18 18 15 14 11 10 9 12 17 14 16 15 14 > 12 Feet (% freq.) 3.7 4.9 3.9 2.0 1.0 0.8 0.2 1.1 1.7 4.0 2.7 3.4 2.5 > 20 Feet (% freq.) 0.2 0.6 0.5 0.2 0.0 0.0 0.0 0.1 0.2 0.2 0.2 0.2 0.2 VISIBILITY (% FREQ.) Visibility <j N. mile 1.9 2.4 3.1 6.1 6.2 4.6 1.1 0.5 0.6 0.9 0.5 1.2 2.4 Visibility <1 N. mile 2.8 3.6 4.1 6.9 7.8 5.3 1.7 0.7 0.9 1.5 0.6 1.6 3.1 Visibility <2 N. miles 3.5 4.7 4.7 8.4 9.9 6.9 2.5 1.4 1.3 2.2 1.1 2.2 4.1 Visibility <5 N. miles 8.2 9.1 11.4 14.9 16.6 15.8 10.3 8.6 4.8 6.2 4.1 5.9 9.7 Visibility <10 N. miles 32.9 32.8 37.1 39.5 48.4 48.0 44.8 43.0 28.9 27.1 24.7 26.2 36.2 + = less than 0.05% Table. 13 Environmental data summary; Offshore Delaware Bay area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Offshore Delaware Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 3.7 4.9 5.6 12.0 13.4 11.2 5.8 2.9 3.4 3.3 2.1 2.9 5.9 Mean number of hours operation of fog signals * 41 61 59 55 41 45 32 22 29 28 21 41 475 Maximum number of hours operation of fog signals for any year (annual only)* 1059 WEATHER & CLOUDS (% FREQ.) Precipitation 6.9 7.9 7.8 5.1 6.0 3.6 4.0 4.2 3.5 5.6 6.3 7.3 5.7 Freezing precipitation 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + Frozen precipitation 1.6 1.5 0.8 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.1 0.5 Thunder & lightning 0.2 0.2 0.2 0.4 1.0 1.5 1.9 1.2 0.7 0.1 0.3 0.0 0.6 Sky _2/8 37.2 38.3 43.5 44.3 45.3 42.3 36.4 40.2 42.9 43.4 39.0 35.4 40.7 Sky overcast (8/8) 31.6 29.1 24.9 23.8 21.5 19.2 21.4 18.8 19.2 25.7 24.6 27.9 24.0 Sky obscured 2.3 3.5 4.5 5.2 7.0 5.7 2.6 1.4 1.0 1.0 0.8 1.1 3.0 Low cloud overcast 23.8 21.2 20.4 16.8 15.4 12.0 11.6 11.2 12.0 18.1 16.3 19.6 16.5 Mean cloud cover (eighths) 4.4 4.2 3.9 3.9 3.8 3.9 4.2 3.9 3.7 3.8 4.1 4.4 4.0 AIR TEMPERATURE (�F) Minimum 3 12 20 32 36 35 61 61 40 39 27 16 3 01% S 18 16 27 36 45 55 64 66 56 45 33 22 40 Mean 39.9 39.8 43.1 49.2 57.3 67.8 74.8 75.4 70.6 61.9 53.6 44.2 56.3 99% < 60 58 60 64 72 80 86 85 83 76 68 62 71 Maximum 75 77 77 80 96 88 93 92 93 99 80 74 99 < 32 �F (% freq.) 23.0 16.3 4.5 + 0.0 0.0 0.0 0.0 0.0 0.0 0.6 10.0 4.5 > 85 �F (% freq.) 0.0 0.0 0.0 0.0 0.2 0.3 2.5 1.0 0.8 + 0.0 0.0 0.4 *Brandywine and Delaware Shoals fog signals + less than 0.05% Table 13 Continued 4 ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Offshore Delaware Bay ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 80 80 81 84 86 85 85 84 81 80 78 78 82 SEA TEMPERATURE (OF) Minimum 30 28 27 33 40 41 59 60 56 50 42 34 27 01% S 33 33 35 39 42 53 64 66 59 53 48 40 47 Mean 45.1 43.4 43.0 46.6 54.1 64.7 73.0 75.1 71.3 64.2 57.7 51.1 57.4 99% S 66 65 64 70 72 78 84 84 81 76 71 68 73 Maximum 80 78 76 80 84 88 90 88 90 84 82 80 90 SALINITY (%O) Minimum 27.1 27.5 27.5 27.3 27.1 26.8 28.6 28.5 27.8 27.7 28.0 28.0 26.8 Mean 31.4 31.4 31.2 31.1 31.4 31.6 31.9 31.6 31.6 31.6 31.5 31.4 31.5 Maximum 34.5 34.1 33.6 34.2 34.6 35.0 34.6 34.1 34.1 34.0 34.1 33.6 35.0 0oD (X0 DENSITY (p) Mean (at)* 23.1 23.2 23.1 23.0 23.2 23.5 23.6 23.5 23.4 23.4 23.4 23.2 23.3 SEA-LEVEL PRESSURE (mb) Minimum 977 980 981 985 995 997 981 976 990 957 981 988 957 01% S 994 990 992 994 1001 1001 1002 1003 1002 998 995 997 997 Mean 1018 1017 1016 1016 1017 1016 1017 1016 1018 1018 1018 1019 1017 99% S 1037 1038 1035 1033 1033 1029 1027 1026 1031 1033 1034 1037 1033 Maximum 1044 1044 1045 1039 1040 1030 1034 1032 1041 1040 1040 1043 1045 * at = (p - 1) X 103; p - gm cm-3 Table 13 Continued. MISSISSIPPI DELTA AREA General Description The Mississippi Delta area is primarily marsh delta land with numerous bayous, canals, and drainage ditches. The natural ele- vations vary from a few feet below to a few feet above mean sea level. The Mississippi River flows in a winding but general south- east direction, emptying into the north central part of the Gulf of Mexico through a number of mouths or passes which, when taken to- gether, form the delta of the river. The shape of the delta is somewhat like the foot of a bird (see Fig. 9), with its four toelike extensions protruding into the Gulf. The passes consist of narrow-banked deposits of sand and clay brought down by the river current which continuously adds them to the seaward margins of the delta. In this manner the delta is being built seaward at an estimated average rate of 300 feet a year. The discolored water discharge from the Mississippi River usually provides mariners with their first indication that they are approaching land. During high-river stages and with northerly winds the discolored water will be encountered in some directions 60 miles or more from land. Numerous oil-well structures and appurtenances are located offshore between the Pississippi River Delta and Galveston Bay, ex- tending as far as the 35-fathom curve, and as far as 70 miles off- shore. 84 91" 900 890 880 870 ... .......... .............. ... ................. ........ ............................ 32" ... .......... I.............X... ......... .. ............................ .. . ..... .... ... . ........ .......................... ........ ......... ........ ..... . ............. ...................................... .... .. ......................... ......... . ........ .... ..... ................................... ............. ....... ............... .. ................................... ............... . ............................ X..... ............................................... :.. . . ........................ .... ........... .... . . . . .. .... ........................ ... ...... ..... ............... . ............ . ...... ................. ................ ............. .. ..................... ....... ......... ..... ...................................... . .... ........... ..... ... ..... .............................. ....................................... ............... .................................. ........... ...................................... ...................................... . .................................... ........ ........ ........ .......... ........ ............ ...................................... ......... ...................................... ........................... .............. ........................................ ...................................... ......................................... ...................................... .......... ....................... ......... ............... I...................... .......... ........ . .......................... .................... .............. ........ ........ ........................................ ......... ......... ............... ......................... ....... ................ ............ .............. .......................................... ................................ ......... ........... ........ ......................................... .............. ......................... ....... .................... I.......... ............. ...... ... . ....................... ...... I.... .................... . ....................... ........ .............................. .... ...... ...... .... ..... ...... . .................. ...... ....... ......... ..................................... ....................... 31 ... ..... .. ... ... ....... ..... 310 :-:-: .......................................... ............... ...................................... ............... ............. ........ . ..... ...................... ............... .. ...... ............................................... ......... ............................. ....... ...... . ........ ... .................................. .... .......... .... ......................... .................... ............... ......................... .. .............. ........ . ...... ........ :-:-: ... .......... .......................................... ...................................... .... ......................... ...................................... ............................ ........ .... ...................... .... ......... ......... ::::: ...................................... ........ .... ........... . ...... ......... .......... .... ..... ... .......... .......... ......... ........ ............................... ... ....... ................. ... .................. ........... ..... ................. ....... ..... ............ ........ .......... ........... ............... 30" 300 New Orlea ..... ... .......... 9 ........ .... X 290 rf 290 Mississippi Delta 280 28" 27- 270 260 26* 910 900 890 881, 870 Fig. 9 Mississippi Delta area map. Periodic tides in the Gulf area usually are small and may, therefore, be greatly modified and sometimes obliterated by fluctu- ations in the water surface due to winds or other meteorological conditions. Along the northern shore of the Gulf from St. George Sound to the Rio Grande the tide is generally diurnal and the mean range is less than two feet,. However, wind generated fluctuations of 3.5 feet below to four feet above the plane of reference are not uncommon. Tidal currents are generally weak in the open Gulf, but at times they are strong near shore, in the vicinities of shoals, and in the entrances to harbors. Wind-driven currents are very complex. Their speeds and directions depend upon a -number of factors such as the speed, dir- ection, and duration of the wind, the proximity of the coast and the orientation of the coastline. THE ENVIRONMENT The climate of the Delta area is influenced by the many water surfaces provided by the numerous lakes, streams, and canals, and by the proximity to the Gulf of Mexico. Throughout the year, these water areas modify the humidity and temperature conditions, de- creasing the range between extremes; when southerly winds prevail, these effects are increased, imparting the characteristics of a marine climate. 86 From June to September, the prevailing southeast to south- westerly winds carry warm, moist air inland. This is favorable for sporadic, often quite localized, development of thunderstorms. From November to March, the area is subjected alternately to tropical air and cold continental air in periods of varying length. From December to May or June, the Mississippi River waters are colder than the air temperature, favoring the formation of river fogs, particularly with weak, southerly winds. With such winds, fog may be encountered anywhere from 60 miles off the Delta passes to the city of New Orleans. Pressure The general circulation of air over the Mississippi Delta area follows the sweep of the western extension of the Bermuda High during the spring and summer months. High pressure systems over the North American continent modify the pattern for the remaining months until spring, when the western extension of the Bermuda High again emerges as the dominant control over the Delta area. The monthly mean pressures range from a maximum of 1020 millibars in December and January to a minimum of 1015 in September. The Bermuda High has greater constancy that the continental high pressure systems so that in late spring and summer it main- tains a rather steady flow of warm moist air which, to a large de- gree, controls the climate over the Delta area during these seasons. Accordingly, spells of good weather tend to be longer during these seasons than during the late fall, winter, and early spring. 87 There is an obvious diurnal pressure variation, with early morning (4 a.m.) and late afternoon (4 p.m.) minima and late morning (10 a.m.) and night (10 p.m.) maxima. This regular pattern is masked at times by the larger pressure changes associated with storms of continental origin and tropical cyclones that reach the area. However, during the more settled weather of the summer and early fall, and during periods of steady weather conditions at other times of the year, the occurrence of a diurnal pressure change is so characteristic that an interruption of the pattern is generally considered to be an indication of a change in the weather and pos- sibly the approach of a tropical cyclone. Extratropical Cyclones Some 30 to 40 polar air masses penetrate the Gulf of Mexico from the North American continent each winter. During the year some 15 to 20 of these bring strong northerly winds to the Gulf area and are called 'Northers." Winds from 25 to 50 knots or more may occur in severe northers of the Gulf. Northers ordinarily occur from November to March. Severe northers usually occur from December to February, but occasionally later. They generally last about a day and a half, but severe storms may endure for three or four days. Tropical Cyclones Of the large number of tropical cyclones originating in the North Atlantic and Caribbean Sea that enter the Gulf of Mexico, combined with those which are born in the Gulf area, many strike some part of the northern Gulf coast. Some of these storms find 88 their way into or near the Mississippi Delta area, causing wind and water damage. Since 1900 the centers of three great hurricanes have passed over the New Orleans area. Numerous other hurricanes have affected the Delta area. In 1965, Hurricane Betsy brought destructive winds to that area and caused over 50 deaths from drowning. Extreme winds of Betsy were estimated at 108 knots. Camille, which struck the area in 1969, was the greatest hurricane ever recorded in North America. Figure 10 shows the tropical cyclone strike zones and proba- bilities for the Mississippi Delta area. The table below shows the frequency of tropical cyclones and hurricanes in the study area outlined on the map in Fig. 9. Total Number Average Number of Years 1886 - 1971 between Occurrences Tropical Cyclones 43 2 Hurricanes 20 4 Great Hurricanes 3 28 Between 1886 and 1971 there were a total of 43 tropical cy- clones in the Delta area. Of these, 20 were of hurricane force and three were defined as great hurricanes. Winds Winds near the Gulf Coast are more variable than over the open waters of the Gulf since the coastal winds fall more directly under the influence of the moving cyclonic storms that are charac- 89 100� 95� 90� 85" 80� 75� 70� 650 50� 50 45- X 4 N-w York 40� 40� CATEGORY MAXIMUM SUSTAINED WIND SPEED TROPICAL CYCLONE GREATER THAN OR EQUAL TO 34_KA[QIS HURRICANE GREATER THAN OR EQUAL TO 6_41~DOTS INTENSE HURRICANE GREATER THAN OR EQUAL TO 108_INQZT&_ 35� 35� 30 New OrleansCL 3Q0 25� 25� 100� 95� 90� 850 80� 75� 700 650 AREA MsissippI a Zonel PROBABILITY (%} OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 18% 5 15 HURRICANE 9% 10 5 INTENSE HURRICANE <1% AREA _MissiJppLsel-a Zone_2_ PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 21% 4 18 HURRICANE 13% 7 11 INTENSE HURRICANE 2% 42 2 AREA Misissippi DeIa Zone 3 PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 15% 6 13 HURRICANE 9% 10 5 INTENSE HURRICANE 4% 28 3 Fig. 10 Tropical cyclone strike zones and probabilities for the Mississippi Delta area. 90 teristic of the continent, especially during the winter season. Along the coast, land and sea breezes prevail, although over the open waters little difference between daytime and nighttime winds is noticed. The higher mean monthly winds in the winter season are a pro- duct of the frequent winter storms that usually follow an easterly path north of the Delta. Occasionally one moves into the area, producing the winter gales. The easterly winds of the Bermuda High, although more con- sistent, are weaker, with a minimum monthly mean occurring in July. However, the strongest winds observed are more likely to occur during the hurricane season. Extreme Winds As sufficient wind observations are unavailable for the Mississippi Delta area, both in time and space, the return values of maximum sustained winds, given in the table below, are primarily statistical estimates. Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 90 kts 100 kts 115 kts 125 kts For example, on the average, there will be a maximum sustained wind speed of 100 knots in the Mississippi Delta area once in every 10 years. Waves The distribution of wave heights is roughly the same as that for the winds, the maxima occurring during the time of strongest 91 mean monthly winds, from October through March. The minimum heights occur in summer. The Delta area has frequencies of waves greater than or equal to 12 feet ranging from 0.1 percent in late summer to 3.2 percent in February. There are some occurrences of waves greater than 20 feet for the majority of months, with a maximum of one-half percent in December. As with the winds, because of insufficient data for a clina- tological conclusion of significant wave heights, the table below primarily reflects a statistical approach. Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 31 ft 34 ft 39 ft 43 ft Visibility Warm, moist Gulf air blowing gently over the Delta area often brings about the formation of fog. With such winds, fog may be encountered some distance off the Delta area. Fog is most common from December to April with little heavy fog in summer. The mean number of hours of fog signal operation at Head of Passes West Jetty points out that the greatest frequency of fog occurrences are during winter over the Delta area. Visibility is reduced during the winter primarily because of fog. Visibility may also be lowered when northerly winds bring the industrial pollution from plants in the New Orleans-area, or when marshlands are burning. Temperature Cold temperatures in winter depend largely on the frequency and intensity of northers. The mean annual temperature for the Delta area is about 75'F, with the monthly mean minimum and maxi- mum occurring in January and the July-August months, respectively. Throughout the year the mean monthly temperatures of the Delta area generally follow the temperatures of the surrounding water areas. Because of this, the area has a subtropical marine climate. There are exceptions, as the range of extreme temperatures is about 90'F. The extremes occur with the warm and cold fronts that pass through the area; and with them, comes the departure from a marine environment. There are few observations in which the temperatures are be- low freezing. However, temperatures usually reach 85'F or greater at sometime during every month of the year, the maximum frequency of occurrence taking place during the July-August period. Precipitation A fairly definite rainy period occurs during the late autumn, winter, and early spring months, and is generally associated with .extratropical cyclones. In summer and early autumn scattered shower and thunderstorm activity is high. The gentle coastal slopes do not, however, give rise to persistent areas of concentrated thunderstorm activity day after day. In general,-the greatest rainfall occurs in summer and early autumn with some of the heaviest falls associated with tropical cyclones during the months of August, September, and October. 93 While thunder usually accompanies summer showers, thunder- storms with damaging winds are relatively infrequent. The most damaging thunderstorms are those associated with cold fronts and line squalls. Hail of a damaging nature seldom occurs, and torna- does or waterspouts are extremely rare. Measurable precipitation occurs on about one-third of the days in winter. Much of this falls to the north of warm or cold fronts which have stalled over the northern Gulf of Mexico. Rain is as apt to fall in one hour as another, generally slow, steady, and relatively continous. At times, winter rainy periods extend over several days. Snowfall amounts are generally small, with the snow usually melting as it falls. The pattern of spring rains is similar to that of winter, while fall rains are distributed in much the same manner as summer rains. Cloudiness Over the Mississippi Delta area cloudiness averages between about 3/8 in May to about 5/8 in December with relatively small seasonal variation. The nature of the cloudiness varies with the season. In winter the area has occasional gray, overcast days but in summer these are rare. Much of the summer cloudiness consists of convective cumulus clouds or high, relatively transparent clouds. There is a considerable variation in frequency of overcast days for the year, with the minimum occurring during the summer and 94 the maximum in winter. Low cloud overcasts and total sky obscura- tions also increase in frequency during the winter months. The greatest frequency of observations having clear skies (equal to or less than 2/8) occurs during the spring period. Relative Humidity The monthly mean relative humidities are high throughout the year, with negligible seasonal variation because of the close prox- imity of the Delta area to the Gulf waters. Maximum values of the monthly means occur during spring, the time of greatest constancy of southeasterly winds. Tides and Currents Tides in the Mississippi Delta area are chiefly diurnal. There is very little tidal variability, with ranges under two feet in all areas. Diurnal Tide Mean Tide Location Range (feet) Level (feet) Pass at Loutre Entrance 29�12'N 89002'W 1.2 0.6 Southeast Pass 29007'N 89003'W 1.2 0.6 Southwest Pass 28�56'N 89026'W 1.3 0.6 Currents to the north of the Delta are generally more swift and steady than those to the south. North of the Delta directions vary from westerly to southerly with average speeds of 1.0 to 1.5 knots. South of the Delta, currents are more steady, flowing to- 95 ward the northwest at an average speed of about one knot. Currents are somewhat weaker and more variable in the spring and summer. Significant storm surges in the Delta region are most often associated with hurricanes. A surge of over 15 feet above mean high water was recorded with the passage of Hurricane Camille. This was highest ever reached in the United States. Surges of nearly equal intensity have been recorded in the past during other great hurricanes. 96 STATION: NEW ORLEANS, LOUISIANA POSITION: 30.ON 90.3W ELEVATION:, 4 FEET NORMALS, MEANS, AND EXTREMES - Temperature Prenryrtaben Relotine Wind & sr tao somber of days~~~~~~~~~~~~etal,.R.-.-b, fd~y heditya N ---aI Exteeren S..., Inn pellets Fastest mile - t0 Os ___ s...5 on~~~~~~.set sMa. ro - M~~~~~~~~~~~~~~~~~~~~~~~~~ >u ea .! - - S a ~~~~~~~~~~~~~ ~~~~~~ ~~~~~~~~~~~~~~~~~~00 06 121 i s a a ~~~~~~~~~~~~~~~;, a & 15 n s.2, - g~~~~ a~ :9 E t I5 laa~ t (L..altime) 2 ~ t . .2 5. a a a n .,,a a n ma na me o~~~~~~~~~~~~ mu o~~~ mu ts ~~~.8 r~~~ ar a.~~~nr n o. 5 24 24 24 24 24 24 24 24 22 22 22 22 22 11 11 22 22 22 22 22 22 22 22 24 24 24 24 (a) (6) (6) (6) (6) (6) 64.4 44.8 54.6 8197 14 1,963+ 363 3.8,4 12.62 1966 0.054 1.968 4.77 1952 Tj T 1969+ T( 1969+ 84:86 67 73 9.6 33 38 1966 6.7 7 8 16 10 0 2 7 0 * 3 0 P 66.7 47.2 37.1 84 1948~~~ 1917+ 28 39 05 99 10 92 5.016 . . 98 2015 28 63 68I10. 43 26 1970 6. 8 6 14 10*2 5 0 0 3 0 8712 51. 61.4 87 1963+ 2616 92 53.41.0 148 0.24 1935 7.817 1948 7 1959 7 1939 823 84 630 65. 10.2 37 1199 .1 8 91 9035 0 0 1 0 A 77 .7 381 679 41 94 38196 39 4.538.78 149 0.33 1963 4.Is 153 0.0 0.0 0.0 85886066 . 5 016 . 1 1 M 84.4 64.4 74.4 96' 19953+ 481 19660 0 4.38 14.233 199 0.9 9 1949 9.8 1959 0.0 0.0 0.0 86 89 6 0 165 8.3.a 31 23 19962 I., 1i1. 11 19 8 0 16 1. 4 0 0 0 (.9 a 9.6 70.3 80.1I100 1954 53 1966 0 4.43 8.87 1962 1.12 1952 4.19 1953 0.0 0.0 0.0 87 90 62 67 7.0 58 27 1962 4.9 10 13 7 10 0 9*17 0 0 0 90.611:1 72.06 61.6 99 1951I 60 1967 0 6.72 11.476 19934 3.45 1951 4.3 1966 0. .. 9 91 66 73 6.4 32 07 1969 6. I3- 16 log 135 0 16 *20 0 0 0 A 073? 8. 100 1951 81968 0 5.34 11.77 193 20 192 306 1969 0.0:O 00.0 D0.0 8992667 6. 42 3296 5. 9 3 9 303 *19 0 0 0 S 87.2 69.3 78 .3 97 19 544+ '42 1967 0 51.03 13.513 19481 0.24 19.53 31.46, .1927 0.0 0. 0.0 87 89 65 7647.5 69 09 1965 3'.2 11 10 9 9 0 7* 9 0 0 0 O 80.3 60.5 70.4 92 19 62+ 35 1968 1 2.84 6.45I 1959 0.00 1952 2.5II 1960 0.0 O., 0.0 84a8759 72 7.58 490 17 1964 4.1 16 7 8 6 0 2 2 1 0 0 0 N 70.3 49.6 60.0 8191 24 1970 192 3.314 14.58 1947 0.21 1949 6.3 9315 1930 N838597 8. 30 31 1969 4.9 12 8 150 6 0 1 4 0 0 1 0 4 5. 455 :5. 86 19705 17 1962 302 4.10 10.77 1967 1.46 1958 3.94 19522 0.1 2.17 '19963 2T7' 99 6 3 83 N6 66 '73 9.2:'Z 32 17 1969 6.1 a 81 10 * 2 3 * 3 0 .JUN lAtN. MAR. OCT. MAY DEC. DEC. SEP. YR 78.2 39.0 68.6 100 1954+ 1.4 1963+ 1385 03.90 19.09 1948 0.00 1952 9.86 1929 0.2 2.7 1963 2.7 1963 85 88 63 70 8.4 69 09 1968 5.6 113 120 132 112 * 68 32 69 * 13 0 Means and extremes above are from existing and -aparable exposures. Annu~al extremes have bee. exceeded at ather sites in the lanality as followsn: Highest tempararture 102 do Jun 1954 and earlier (City Offine); lowest temperature 7 in February 1899; maximum monthly precipitatian 25.11 in Octabor 1937; matnimutm precipitation in 24 hours 14.01 in April 1927 ; awai.nu mothly snowfall 8.2 in February 1895; maxisramn snowfall In 24 hours 8.2 in Februry 1895. tl L.ogi at rend. years,. Onoert --- Uonr dana. t.intes aerIse 1todtnrd dtmen1utniat . nenousd li rhto Wiedtet cue: Itemperamn to deroF; & Fgure tesred at tersr to a d-tretn -nalmo todtuat ditaenttn to tem of degreess frm er Po Other muorh map be.. tar mor orle towe year 5 rectt..n., t09alo -owal toK tores wt- mavmee 27 m-n pent hose -o netv hmdtt Le. 0- Eat O-Suh2-Ws,3 Hrh n eCohn. ttoolr.s w~dn, t t enro mo- of ther hano I... heerk = .to'he reud-". - ta poror.Hoin ro day nlo are the -so at neagtte drpartro n5 -veag daIly rope.- wLed dtrattao sod speeda diuded by rh. .umber nt eho-ootu. If ftgao oppoar to the dtrodno tl Cliartoo. a I tan:dard -ocsut (1931-1960t. f ootenm 65' F. Coelto deoneo day ..I.t s-n lb. same of pootne daperere of anorag dotty notom aedor "Faenosr mite ma .. enroedopeed.. oretrest ohoe-er 1-Isrevte.. o aa hoo.hl. trprcre Ifa 65 F. Steer ... tonadod hr W ginningl roat btotst ay 1940. Th. Inrm + Aho noos-11e dates, mooths, or Yesr. Ir pettero"I tentuder mild raleo of I.. totet) aod pentnta. nsoto at.oo petter esusoed T Tran, so amee ma -11i Co moasune . tea hobyer ut tue. B."v ftu reduce Itotily u 1/4 U.l or tore. Below oer -eprror pended bycmeats Th. prevantog dlrcrt ar weed torh Homlb- Sky nuse to exp-esed tocruo.ga of I5- fo flu udo ar ah-Irtg poherurme ro 10 for oplter shy Mean,~~~~~~~1 ar ee nhet rm. re-odo ehegh ounc. Th. somber otolear dapo I. bae .. aceg clorrinesa 0-3, perly cloudy days 4-7, sod 1903. cloudy dayr B-10to rerro * ; 70' at Alakaw ototfs. Solar radaslus dan -r the aeaunderadidff..r rodtaluoe hertoera sorgac Th. boob1y deoure -a gram rotot Per tru-c -eMlacer. Table 14 Land station climatological data summary for NEW ORLEANS, LOUISIANA. ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Mississippi Delta ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01%S 3 3 3 4 2 1 2 2 2 3 3 4 3 Mean 14.1 14.2 13.6 12.4 10.5 9.2 8.2 8.5 11.9 12.7 13.5 13.7 11.9 99% S 38 39 32 32 28 28 22 28 32 32 33 33 31 Maximum observed (1871 - 1971) Winds of 175 knots are estimated to have occurred south of the Delta during Hurricane Camille. > 34 Knots (% freq.) 1.2 1.2 0.7 0.4 0.1 0.1 0.1 0.1 0.5 0.7 1.0 1.0 0.6 > 41 Knots (% freq.) 0.2 0.1 0.1 0.1 + 0.1 0.1 0.1 0.2 0.2 0.1 0.1 0.1 Prevailing direction E SE SE SE SE SE SE E E E E E E WAVES (FEET) 01% S 0 1 1 0 0 0 0 0 0 1 0 0 Q( Mean 4 4 4 3 3 2 2 2 3 4 3 4 3 00 99% S 17 16 12 10 9 8 7 7 12 14 12 14 12 > 12 Feet (% freq.) 2.2 3.2 2.0 0.4 0.5 0.2 0.1 0.1 1.6 2.6 1.2 1.8 1.3 > 20 Feet (% freq.) 0.1 0.1 0.1 0.0 0.1 0.1 0.0 0.0 0.1 0.2 + 0.5 0.1 VISIBILITY (% FREQ.) Visibility <4 N. mile 0.5 0.3 0.6 0.3 0.1 0.1 0.1 0.1 0.1 0.2 0.1 0.2 0.2 Visibility <1 N. mile 0.7 0.4 0.7 0.4 0.1 0.2 0.2 0.2 0.3 0.2 0.2 0.3 0.3 Visibility <2 N. miles 0.9 0.7 1.1 0.7 0.3 0.3 0.4 0.3 0.5 0.4 0.4 0.5 0.5 Visibility <5 N. miles 2.0 2.4 3.0 2.1 0.8 1.0 0.9 0.8 1.7 1.0 1.2 1.5 1.5 Visibility <10 N. miles 12.9 17.4 20.8 17.9 10.4 7.9 5.9 7.0 12.6 9.0 10.3 12.4 12.0 + - less than 0.05% Table. 15 Environmental data summary; Mississippi Delta area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Mississippi Delta ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 1.2 1.2 2.1 1.1 0.2 + + + 0.1 0.1 0.2 0.5 0.6 Mean number of hours operation of fog signals * 156 148 171 103 13 4 5 4 9 9 38 100 760 Maximum number of hours operation of fog signals for any year (annual only)* 1452 WEATHER & CLOUDS (% FREQ.) Precipitation 3.2 4.3 2.7 1.9 1.7 1.9 2.8 3.2 4.1 2.9 2.9 3.6 2.9 Freezing precipitation 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Frozen precipitation 0.0 + + + + 0.0 0.0 + + 0.0 + + + Thunder & lightning 0.6 0.8 1.0 0.9 1.0 1.7 2.8 2.3 1.6 0.8 0.6 0.5 1.2 Sky <2/8 29.1 30.4 33.9 39.9 45.3 39.8 31.5 31.6 27.3 38.2 34.6 27.8 34.1 Sky overcast (8/8) 25.1 25.3 20.8 15.6 9.8 8.4 9.2 9.4 14.8 11.4 17.0 22.6 15.8 (.O Sky obscured 0.7 0.8 0.7 0.5 0.2 0.2 0.2 0.2 0.3 0.2 0.4 0.7 0.4 Low cloud overcast 16.0 15.6 11.8 7.4 4.2 2.6 2.8 2.7 5.9 5.3 9.3 12.9 8.1 Mean cloud cover (eighths) 4.8 4.6 4.3 3.8 3.3 3.5 3.9 3.9 4.3 3.7 4.1 4.7 4.1 AIR TEMPERATURE (�F) Minimum 15 10 25 36 45 56 62 67 50 38 26 18 10 01% 43 45 49 58 66 73 75 75 71 60 51 46 59 Mean 65.4 66.1 68.1 72.5 77.7 82.3 83.9 83.9 82.1 77.3 71.5 67.4 74.9 99% < 79 81 81 83 89 91 92 93 91 87 82 81 86 Maximum 88 88 88 92 95 97 100 100 100 96 91 86 100 < 32 �F (% freq.) + + + 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + + + > 85 F (% freq.) + 0.2 0.2 0.9 4.7 17.9 36.9 36.2 18.5 4.1 0.6 0.1 10.0 * Head of Passes West Jetty fog signal + = less than 0.05% Table 15 Continued ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Mississippi Delta ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 76 77 78 79 79 78 76 77 78 74 75 76 77 SEA TEMPERATURE (�F) Minimum 45 39 45 53 62 67 67 72 70 68 58 52 39 01% S 57 56 58 65 70 76 80 80 78 73 65 62 68 Mean 71.4 70.4 70.9 73.2 77.9 82.4 85.0 85.4 84.2 81.1 76.8 73.5 77.7 99% S 81 80 79 81 83 87 90 91 88 86 83 81 84 Maximum 86 86 88 88 92 94 94 94 94 90 90 86 94 SALINITY (%o) Minimum 11.6 0.0 2.6 14.0 4.3 5.4 3.8 12.7 19.6 18.7 21.4 16.9 0.0 Mean 30.2 27.3 26.9 25.0 22.5 23.8 26.8 28.0 28.2 30.1 32.7 31.9 27.8 Maximum 37.9 36.3 36.3 35.0 34.5 38.1 37.1 38.8 34.2 35.8 36.7 36.3 38.8 DENSITY (p) Mean (ot)* 21.1 26.8 26.2 24.2 21.4 21.5 23.3 24.1 24.8 19.2 22.1 22.1 21.1 SEA-LEVEL PRESSURE (mb) Minimum 997 995 998 980 990 978 999 999 981 998 992 976 976 01% S 1007 1003 1004 1004 1006 1007 1009 1009 1004 1005 1007 1008 1006 Mean 1020 1018 1017 1017 1016 1016 1017 1016 1015 1017 1019 1020 1017 99% S 1033 1032 1032 1029 1025 1022 1025 1025 1024 1027 1030 1034 1028 Maximum 1037 1041 1033 1032 1029 1031 1030 1031 1029 1035 1035 1037 1041 *at - (p -1) X 103; p- gm cm-3 Table 15 Continued GALVESTON, TEXAS AREA General Description The Galveston, Texas area (see Fig. 11) is located in the flat Coastal Plains on the northwestern shores of the Gulf of Mexico. The city is located on one of the many barrier islands found along the Gulf coast. Galveston is protected on the Gulf side by a concrete seawall 17 feet high. Northeast of the island is the channel entrance to Galveston Bay, the approach to the cities of Galveston, Texas City, and Houston. Galveston Bay is a large irregularly shaped shallow body of water and, except for the Federal Project Channels which range in depth from 36 to 40 feet, has general depths of seven to nine feet. Galveston Jetty Light, 91 feet above the water and equipped with a fog signal and radiobeacon, marks the entrance to the Bay. A considerable number of unmarked dangerous wrecks exist in the Gulf Approach to the Bay. Deep water extends fairly close inshore along this section of Gulf shore. The 30 foot isobath ranges from about one and one-half to four nautical miles seaward. Asystem of shipping safety fairways exists along the Gulf Coast to provide safe lanes f or shipping that are free of oil well structures. The effect of the wind on the water level in this part of the Gulf and adjoining bays may be considerable. A level two to four �01 970 960 950 940 930 320.320 . . . . . . . . . 31 31 3o Galveston 290 Galveston, Texas 28/ 280 270 270 260 260 970 960 950 940 930 Fig. 11 Galveston, Texas area map. 102 feet above mean low tide may result from a strong wind blowing con- tinuously for several days from the east and southeast. A strong wind blowing steadily from the north for several days may lower the water to a level two or three feet below mean low tide. The diurnal range of tide at Galveston Bay entrance at the south jetty is 2.0 feet. The currents are also modified frequently by the winds. Easter- ly or southeasterly winds may cause a continuous flood current be- tween the jetties at the entrance for a period of a day or more, and westerly or northwesterly winds sometimes set up continuous outgoing currents for a similar period. The average velocity of the current between the jetties (at strength) is 1.7 knots on the flood and 2.3 knots on the ebb. The current outside the jetties frequently has a velocity exceeding one knot. The set may be in any direction under the combined influence of the entrance currents and currents setting along the coast. THE ENVIRONMET The climate of the Galveston area is predominantly marine, with periods of modified continental influence during the colder months when cold fronts from the northwest sometimes reach the coast. Because of its coastal location and relatively low lati- tude, cold fronts which do reach the area are very seldom severe 103 and temperatures below 32'F are recorded on an average of only four times a year at Galveston. Throughout the year, the Gulf waters modify the humidity and temperature conditions, decreasing the range between extremes. From November to March, the area is subject alternately to tropical and cold continental air in periods of varying length. From June to September, the prevailing southeast to southwesterly winds carry warm, moist air inland. This is favorable for the development of thunderstorms. Pressure During the spring and summer months the western extension of the Bermuda High dominates the general circulation of air over the Galveston area. The North American continental high pressure systems modify the pressure pattern for the remaining months. Winds of the Bermuda High have a greater constancy and, therefore, greatly influence the climate of the area with its steady flow of warm, moist air. Such influences have a tendency to produce longer periods of good weather. The monthly mean pressures vary from a low of 1015 millibars in late spring to a high of 1020 millibars in winter. Extratropical Cyclones Of the 30 to 40 polar air masses penetrating the Gulf of Mexico each winter, some 15 to 20 bring strong northerly winds. These 'Inorthers" occur from November to March. The winds, although occasionally blowing with a speed of over 35 knots, are not dan- 104 gerous to vessels anywhere close to the coast, as they blow of f- shore and the sea is not heavy. Charts of mean extratropical cy- clone tracks appear in Appendix B. Tropical Cyloes Of the many tropical cyclones observed in the Gulf of Mexico a few find their way to the Galveston area. The area has been subjected to major tropical storms of hurricane force at infre- quent intervals. The 1900 hurricane completely destroyed the city of Galveston, but the building of a 17 foot seawall on the Gulf side of the island afterwards reduced the danger of direct wave and swell action associated with this type of storm. These storms are dangerous to shipping near the coast because the wind is onshore. Fig. 12 displays the tropical cyclone strike zones and proba- bilities for the Galveston area. The table below shows the fre- quency of tropical cyclones and hurricanes in the general study area outlined on the map in Figure 11 (see Appendix A for coordinates). Total Number Average Number of Years 1886 - 1971 between Occurrences Tropical Cyclones 29 3 Hurricanes 15 5-6 Great Hurricanes 3 28 IThe table shows that between 1866 and 1971 there were a total of 29 tropical cyclones in the Galveston area. Of these, 15 were of hurricane force and three were considered to be great hurricanes. 105 100� 95� 90� 85� 80� 75� 70' 65� 50� 500 4.45� """'45 New York 40� 40� CATEGORY MAXIMUM SUSTAINED WIND SPEED TROPICAL CYCLONE GREATER THAN OR EQUAL TO 34_-KNQIS HURRICANE GREATER THAN OR EQUAL TO 6_41_LOTS INTENSE HURRICANE GREATER THAN OR EQUAL TO 109_KlNQIS 35� ' 35� 30 New OrleansC 30� 25� 25' 100� 95� 90� 85� 800 750 700 650 AREA Galvestol PROBABILITY (%) OF AVERAGE NUMBER TOTAL NUMBER OCCURRENCE IN ANY OF YEARS OF OCCURRENCES ONE YEAR BETWEEN OCCURRENCES 1886-1970 TROPICAL CYCLONE 20% 5 17 HURRICANE 12% 8 10 INTENSE HURRICANE 4% 28 3 Fig. 12 Tropical cyclone strike zone and probabilities for the Galveston area. 106 Winds The prevailing winds are northerly from November through Jan- uary, throughout which time "northers" occur frequently. Although winds greater than 34 knots are observed for each month of the year, the greatest frequency is during the winter months. Land and sea breezes prevail along the coast, while little difference between daytime and nighttime winds are noticed over the open waters. The lowest monthly mean winds occur during the summer months,, with the prevailing easterly winds of the Bermuda High. Extreme winds for the year, however, are likely to occur during the late summer-early fall, which includes the hurricane season. Damaging winds are relatively infrequent in summer thunderstorms, but are sometimes associated with winter cold fronts and squall lines. Extreme Winds As sufficient wind observations are unavailable for the Gal- veston area, the return values of maximum sustained winds, given in the table below, are primarily statistical estimates. Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Maximum Sustained Wind 75 kts 85 kts 95 kts 105 kts For example, on the average there will be a maximum sustained wind speed of 85 knots in the Galveston area once in every I10 years. 107 Waves The distribution of wave heights follows the winds for the Galveston area, as expected. Waves of heights greater than 12 feet are observed for all months of the year but August. Some have pro- bably occurred during August but were not observed. The greatest frequency of high waves occurs from September through February. There are observations with wave heights greater than 20 feet only during the October, November, and January months. As there are insufficient data for a climatological conclusion of significant wave heights, the table below shows a statistical estimate of high wave occurrences. Mean Recurrence Interval 5 yr 10 yr 25 yr 50 yr Max. Significant Wave Ht. 29 ft 32 ft 37 ft 41 ft From the table it can be expected that there will be one occur- rence having, on the average, a significant wave height of 32 feet every 10 years. Visibility There are occurrences of fog throughout the year, the greatest frequencies taking place from December through April. Fog is the primary cause of reduced visibility, as these same months also re- flect the highest percent frequencies in which visibility is legss than five miles. The monthly mean number of hours in which fog signals operated at Galveston Channel Light reflects this long season of relatively foggy days. 108 The close proximity of the Gulf waters and the Bay of Galveston enhances fog occurrences there. An average of 16 days a year have heavy fog in the city. Temperature Temperatures are moderated by the influence of winds from the Gulf, which results in mild winters and relatively cool summer nights for the Galveston area. However, polar air penetrates the area frequently enough to provide stimulating variability in the weather. A record low temperature of 8'F occurred in February 1899 in the city of Galveston. The annual mean air temperature of the marine area of Gal- veston is about 74'F. There is an annual mean range of about 21'F with the mean low occurring in January and the mean high occurring in July and August. The extremes out over the water range from. 10 to 100'F for the period of record. There are few occurrences of freezing temperatures, and these are confined to the months of November through March. On the other hand, all months but December and January had temperatures greater than 85'F. Precipitation Mean monthly rainfall is rather evenly distributed throughout the year. The greatest frequency of precipitation occurs during the winter months, coming mainly from frontal activity and low stratus clouds, the latter producing slow, steady rains. Precipita- tion may occur at any hour, and may continue intermittently for several days. � 09 Amounts of rainfall during the summer months may vary greatly over the Galveston area, as most of the rain in this season is from local thunderstorm activity. Hail is infrequent because the neces- sary strong vertical lifting is usually absent. Tornadoes and waterspouts are rare. Cloudiness Cloudiness over the Galveston area averages between about 318 in June to about 5/8 in December and January. The nature of the cloudiness varies with the season, with winter having occasional gray, overcast days and summer consisting mainly of convective cumulus clouds. It follows that the percent frequency of overcast skies is greatest in winter and smallest in summer. The degree of obscured skies also follows this annual cycle. The greatest frequency of observations having clear skies occurs during the late spring period. Relative Humidity_ High humidities prevail throughout the year, with little sea- sonal variation. This is because of a rather evenly distributed annual precipitation pattern And the availability of water vapor from the Gulf surface. Maximum values of the monthly means occur during spring, the time of greatest constancy of southeasterly winds, which bring moisture from the Gulf. Tides and Currents Tides in the Galveston area are predominantly diurnal with ranges of-two feet at the South Jetty (29020?N 94'42'W) and 1.4 110 feet at the ship channel (29�19'N 94�48'W). Mean tide levels are 1.0 and 0.7 feet, respectively. Currents off Galveston are generally light and variable, averaging about one knot in winter, somewhat less in summer. Diurnal tidal currents at the Galveston Bay entrance (29021'N 94042'W) are 1.7 knots toward the WNW at flood and 2.3 knots toward the ESE at ebb. Significant storm surges are most often related to the passage of hurricanes. Surges of nearly 14 feet above mean high water have occurred with the passage of great hurricanes. Ten foot surges have been recorded during the offshore passage of intense hurricanes. STATION- GALVESTON, TEXAS POSITION: 29.3N 94.8W ELEVATION: 7 FEET NORMALS, MEANS, AND EXTREMES Tompeestore ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ ~~Precipitation Remaove Wind &nMean number of days humidity Nasma Extremes SoP.eeptet. atest mite to N~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Z" a aO.u a ~ us, 0 a aa u~~~~~~~ta a ~ ~~ ~~~~~~~ ~~~~ ~~~ ~~~~~~ E . -5 Z 8 ! . 2' a a .a- Aa II-4: 5 a9 7 7 199to .1 80.3 49.3 54.9 77 1969 11~~~~~~ ~ 18886 300 3.46 10.39 1899 0.02 19509 3:.38 1923 T2 0.9 194D 0.9 1940 84 80 77801. 23 S 90 490 50 * 2 0 P 62.4 81.2 16. 83 1932 8 189 208 2.88 8.291881 0.09 1954 6.55 1932 0.2 5.4 1895 15.4 893 83 84 74 7 11.8 6952 192 35 9 * a 06* 1 N 66. 562 61. 85 1879 27 1943 18 9 2.86 9.39 1926 0.06 1933 4.58 1944 T 1 19307 T I932 8438 74 79 11.9 00 08E 1 9 572 56 8 5 0 * a A 73.0 64.0 66.5 92 1953 38 19 38 30 2.3,9 11.04 1904 0.01 1887 9.223 1904 0. a. 00 86 86 73 5 SO.1 07 NW 11961 6165* 0 0 0 0 0.1 71.3 75.8 93 191 52154, 2.79 105 929 T 189 .13 1916 0:.0 0.00 838 73 770 912 66 8199 6 6 5 * .1 85.6 77.7 81.7 99 1918 57 1903 0 2.60 15.49 1919 7190.7 12.56 1961 0.0 D.0.0 0 So1 70 73 10.7 62 E112 766 51 0 0 0 8 7:.5 7.8. 83.1 101 19232 66 1910# 0 4.79 18.174 1900 7 91962 14.35 1900 0.00 0:00 80 St 70 73 9.: 8 68 NW 11943 72 9? 5 41 0 0 0 & 87.3 79.0 83.3 100 1924 67 1966+ 0 4.39 19.08 1915 0.00 1902 9.03 1915 0.0 0.0 0.0 79 81 69 73 9.4 91 0 1913 717' 1 69 79 9.55 0a00 0 7 4. 75.5 80.1 96612 32 142 3 .9260 185 0j.041924 1.8 96 0.0 0.0 0.0 78 I16 51. 0 E10 991 0 0A85 684 7. 94 192 112+ 0 28 77 81 7 15+1.10 M90 0.0 . . 768637 10.3 66 SE 190049 72 6 0 0 5 0 N 8. 87. 630 8 1886 26 191 18 35 61 90 00 93 90 90 0. . . 28 27 12 0 90 6 0 * 0 D 62.7 81.6 57.2 80 18916 186 1988Is0 270 3.896 110.28 11887 0.23 18839 3.43 1964 7 0.2 1924 0.2 1924 BB 86 77 80 11.3 5 -815 91 JUL.I :88. SEP. 650. JUL. 988.; FEE. 0 S0 E9P.9614 YR 74.5 65.1 69.9 101 1932 8 189 1235 41.81 26.01 1883 a.00 1902 14.3.5 1900 0.2 15.4 is9 13.4 LB890 S183 7Z 76 11.0 10 IE 100 6496 *1 * 4 0 0 100 m.p.h. recorded at 6:15 p.m. Sept. 8 just before nemometar blew wawy. Mlamirr velocity estimated 120 from NE between 7:30 end 8:30 p.m. s) Laagth of meud. yeses h . Mod am ....sy data. riotou otremsetdleutad, dimessLanal ..ft. aoed to Oths hutiotuoac: topoesa- O do area P.; & Prances Instead of Iletters tea dierto.I. -otI- MMtet dlmeerroo in rena at dom Imum I-so North; Othe moeths rsy be far mor am fewoc yeae If pr i.tatr. InldIng ,anat toohos; mta mooe..a ie pee hooc; sod colatv humidity La.., 09-E-us, 10- Sosh, 27-West,,S 3- Norrb, and'S- Cal. Rslat idi.Oeveacmo thoe.bn hoes heed to.. oh aod, t aco. Heao Ill, dem da alb. ar-heam of neaatlo dep.come of ovecaae dully tomomu midlteestons and upoeda dtnded by the nashe of obae-atoas. If flasce spp-s lath. dreecrln M6 irmannta etmadmamt 1931- 19601. tae 1rm60 . Ca,, ro =I ne day total uc rho auma of dpoar -- doasc of R araedly ..I... uder Poaeo mkl" the cocropoodlea syoedo ac footern obanmd 1W-maevlus roaoe m af. seprme Fin6 p. Stee was Included toansfl orotla belan8 Ith July 1948.Thter + Also on eamlto dase, morebs.or years. Icep.,oa Incadee .olId gets ftn 0001ad a.i.acaas of ofsaIrler aa . Truh16. T Trace, as amosor too oman to .mur..fo . In rhen laye of Ice. Hevy foe cedocea v1.ot,111ry to 1/4 mIlo or I.... Below --e reperatomos ac pendad by amlusiar..1 # T. 8 comp.sa poinuts only. The mmmv.rttoa dImenIon for mtad Ia sh. o=Mcas Sky enoe to eWmoosed Ins ma-9 of ft foe no clouds am obscuring phemens to 100a nmlmo oby Me-o, sod E=-e-m- Midlo I. from emanda Ibeoh ...e,. Th. number of olea days Is bet.ed aas -raa claudi.esa 0-S. y.acly cloudy dso P4-7, an 1963. cloudy dyn 8-t toth. $ 70' t1 Alaksm shtotio. OSlom modisrio data ace the avoaea .of di-ec.ad diffone rdIsstoans -Loelsnta oTha. Tbo lanly deno tes se aSom naloet per sq-s ne-t~ree. Table 16 Land station climatological data summary for GALVESTON, TEXAS. STATION: HOUSTON, TEXAS POSITION: 30.0N 90.4W ELEVATION: 96 FEET NORMALS, MEANS, AND EXTREMES� T..p .. t- P-ipit~fi.Iemature Wind& a Mean number of days Temperature Precipitation humidity . Sunrise Temperatures Nom a l ~~Exte.... !~ ~Sowleplet Fastest mile et Max. Mn ;-3 1 P ~~~~%"g 12 E 1. .2 -. !1 I i ' . 4 99 ~~ El 2 24' z -i 9 9 36 30 36 36 36 36 8 8 8 8 20 15 6 6 7 20 20 20 20 36 36 30 23 a a a a (a) (b) (b) (b) (b) (b) 63.6 q3.6 53 6 83 1967. 17 1963. 384 3o70 10.:1 1944 0.86 1952 3:66 1944 0.2 3.1 1949 3.1 1949 8 184 64 67 11.9 NNW 32 33 1964 47 760 7 4 20 11 2 2 7 0 a 6 0 JF 55.~ 46.01 ~S,8 87 1962 2� 1963 288 3,aa 11,33 1959 0,09 1954 5.03 1966 0.2 4.4 1960 4.4 1960 81 84 60 63 12:1 SSE 40 36 1903 65 5 46:0~ ~ ~ ~ 1 1 9 5 9 1 a1 4 0 36 196634. 5~~~~~~~6 6,7 7 .S 16 10 � 6 0 0 3 0 M 71.7 50.8 61.3 83 1967 P8 1965 192 2*67 11.32 1957 O.07 1953 3.00 1957 T 1*0 1969 1o0 1968 8a6 59 62 12.7 SSE 35 30 1968, 57 6*8 6 1 2 a 6 0 0 1 0 A 78e0 59.0 0685 93 1963 38 1962 36 3.24 8.07 1957 O*061937 S.18 1966 0�0 0�0 0.0 8689 63 68 13.0 SSE 38 16 1966/ .54 760 7 5.7~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0 0. 7 I 4 0 M 85,7 66.2 76.0 94 1907 52 1967 0 4.32 13-24 1968 T 1 937 6.B5 1908 0*0 0*0 060 87 90 61 66 11.7 SSE 41 17 1968 62 6.4 5 13 13 80 7 2 6 0 0 0 4 91.1 72*0 81.6 100 1963 59 1964 0 3*69 1 66 1960 0*08 1934 8.11960 0*0 0.0 I IO 88 l 16�10.2$SE 4& 171965 72:.6 6 17 : I 66 960 1934 8: 0 0 8:0 91 0 2 SS 44 17 1967 1797 0 0 0 0 J 92ol 73.8 a830101 1964 64 1967 0 4.29 12.38 1942 0.07 1962 6.34 1943 0�0 0*0 a *0 88 91 59 64 8II S 40 36 1964 74 59 A 92a8 73.6 83*2 2O6 1962 64 1967 0 4227 18~I 1945 0308 1956+ 15e65 1945 0o0 0o0 0*0 87 91 59 04 0o4 SSE 54 19630 0 A 6 0 4 0 0 : a 34 34 963 ~~~~~~~~~~~~ ~~~~~~70 5e7 8 15 8 9 0 9 26 0 0 0 SB9*9 69.3 79.2 98 1963 50 1967 0 4.26 15.40 1956 0.11953 5.62i94 0 0.0 0.0 0.0 85 88 60 61 31 0 02.3 60*4 71.4 90 1962 38 1964 6 3.772231 1949 T 1952 10.251949 a.0 0.0 00 8386 2 63 9.8 ES 35 31 1967 73 4.7 12 10 9 70 3 4 3 o 0 0 M 71.1 50.5 60.8 88 1963 32 1960 183 3.66 14.36 1946 0.18 949 7�8 1943 0.0 0a0 0.0 8060 68 9112 SSE 30 14 1963 60 5.8 9 880 2 5 0 0 D 65.4 45*9 55.7 82 1964 19 1963 307 4.36 9�80 1949 0.78 19S8 4.39 1964 T T 1961+ T "961+ 81 84 64 69 11o3 SSE 35 31 1968/ 50 6.7 a I8 0 2 6 0 I 4 0 AUG. JAN . OCT. OCT. AUG. FEB. FEB. AUG. YR 79,0 59*3 69.2 106 1962 17 .963+ 1396 45,95 22.31 1949 T 1952+ 1.5.6. 1945 0.4 4t4 1960 4,4 1960 84 87 60 66 10.B SSE 54 34 1963 62 6,2 B7 126 152 103 * 59 42 95 * la 0 0 For record August 1960 through 1968. Means and extremes above are from existing and comparable exposures. Annual extremes have been exceeded at other sites in the locality as follows; Highest temperature 108 in August 1909; lowest temperature 5 in January 1940 and earlier; fastest mile of wind 84 from Northwest in March 1926. (a) Length of record, years based on $anuary data. Unless therwi.e indicated, dimensional units used in this bulletin are: temperature in degrees F.; & Figures instead of letters in a direction co lumn indicate direction in tens of degrees from true Noth; Other months may be for more or fewer yearsif precipitation. including snowfall in inches; wind movement in mles p er hour; andreistirehumidity i.e.. -E-,ast. Is- Suth. 27-West. 36-North. and 00-Calm. Resultant wind s the vector sumof there have been break in the record in prcent Heating degree day totals are .e sums of negative departures of average daily temper- wind directions and speeds divided by the number of observations. If figures appear in the direction h) Cllmato-lal standard no1rm .a (1931-1960). tures from 65' P. Coolng degree day total* are the sums9o positive departures of average daily column under "Fastest mile." th cortespending speeds are fastest observed l-minute value& (be) Less than one haff. temperatures from 65' F. Sleet was Included i snowfall totals beglnrdng with Suly 1948. The term + Aloon esther date, m onthsoryears. "Ice pellets" includes solid grains of ice (e-aet) and paricles consisting of snow peP.eR. encased T Trsce, snsmoun tooTsma.Ure.sure. in a thin layer of lce. Heavy fog reduces visibllity to 1/4 mleor less. Data from William P. Hobby Airport through 1968, Srnmary for the Below ero temperatures are preceded by amlnussi. r Intercontinental Airport will be published when sufficient data The .evln direction for ind in the Norm- Sky cover is expressed in a range of I ph 10 for complete sky M.."f- -d. t-ah -~.Th. b- f.1.. d~y I. .. .. -S. 1..d- 0-, p.Iy 6dy d. 4-. -dhave been accumuulated. See next page for normls applicable to Means, and Etrmesc table is from records through cover. The number of clear days is based on average cloudiness 0-3, pertly cloudy days 4-7. and a be clnaed e x pg o rms pial t 1960. cloudy days 8-10-enths, the observation site at the Intercontinental Airport. 7018' a Aihhn �trtlmu. Solar radiation data are the averagesofdirectand diffuse radiation on a horizontal surface. The Langley denotes one gram calorie per square centimeter. Table 17 Land station climatological data summary for HOUSTON, TEXAS. ENVIRONMENTAL DATA SUMMARY (PART 1) AREA: Galveston, Texas ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN WIND SPEED (KNOTS) 01% S 3 3 3 3 2 2 2 2 2 2 3 3 3 Mean 13.7 13.6 12.9 12.6 11.5 10.4 9.2 8.9 11.7 12.3 13.8 13.8 12.0 99% S 39 39 32 31 29 28 28 28 32 32 33 35 32 Maximum observed (1871 - 1971) Winds in excess of 100 knots are estimated to have occurred during great Hurricanes. 2 34 Knots (% freq.) 1.2 1.2 0.7 0.3 0.2 0.2 0.1 0.1 0.8 0.5 1.0 1.2 0.6 > 41 Knots (% freq.) 0.2 0.3 0.1 + + 0.1 + 0.0 0.5 0.1 0.1 0.2 0.1 Prevailing direction N SE SE SE SE SE S S E E N N SE WAVES (FEET) o1% S 0 0 1 1 0 0 0 0 0 0 0 1 i Mean 4 4 3 3 3 2 2 2 3 3 3 3 3 99% _ 13 12 10 10 9 8 7 8 12 12 13 12 11 > 12 Feet (% freq.) 2.2 2.2 0.7 0.3 0.4 0.1 0.1 0.0 1.6 2.0 1.4 1.4 1.0 > 20 Feet (% freq.) 0.1 + 0.0 0.0 0.0 0.0 0.0 '0.0 0.0 0.4 0.2 + 0.1 VISIBILITY (% FREQ.) Visibility <' N. mile 1.6 1.2 1.7 0.8 0.2 0.2 0.2 0.2 0.3 0.1 0.3 0.7 0.6 Visibility <1 N. mile 1.8 1.5 2.0 1.0 0.3 0.4 0.2 0.2 0.4 0.1 0.5 0.9 0.8 Visibility <2 N. miles 2.5 2.5 2.7 1.6 0.6 0.6 0.3 0.3 0.5 0.2 0.6 1.6 1.1 Visibility <5 N. miles 5.2 5.2 6.6 4.8 1.8 1.9 0.8 0.6 1.3 0.8 2.0 4.1 2.9 Visibility <10 N. miles 23.2 25.0 30.1 29.1 16.5 7.9 6.0 6.3 10.4 10.7 16.3 22.3 17.0 + = less than 0.05% Table. 18 Environmental data summary; Galveston, Texas area. ENVIRONMENTAL DATA SUMMARY (PART 2) AREA: Galveston, Texas ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN FOG Occurrence of fog (% freq.) 3.8 3.5 4.6 3.3 0.8 0.1 + + 0.1 0.1 0.9 2.0 1.6 Mean number of hours operation of fog signals * 105 72 86 37 3 3 2 4 4 8 27 78 429 Maximum number of hours operation of fog signals for any year (annual only)* 697 WEATHER & CLOUDS (% FREQ.) Precipitation 3.6 3.9 1.9 1.6 1.4 1.8 1.9 2.6 3.1 2.1 2.8 4.5 2.6 Freezing precipitation 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Frozen precipitation 0.0 0.0 0.0 0.0 + 0.0 0.0 0.0 0.0 + 0.0 0.0 + Thunder & lightning 0.4 0.7 0.4 0.5 0.9 1.2 1.3 1.5 1.7 0.8 1.1 0.7 0.9 Sky S2/8 29.6 33.1 31.1 33.6 39.4 40.1 33.7 33.6 33.5 42.2 34.5 29.0 34.5 Sky overcast (8/8) 26.9 28.8 23.9 21.8 11.8 6.5 7.9 8.9 12.7 12.7 21.2 29.4 17.7 Sky obscured 2.1 2.3 2.4 1.4 0.2 0.3 0.1 0.1 0.6 0.2 0.7 1.6 1.0 Low cloud overcast 20.8 19.1 16.5 11.5 4.9 2.3 2.4 2.9 4.9 5.9 12.0 17.8 10.1 Mean cloud cover (eighths) 4.9 4.6 4.7 4.3 3.7 3.4 3.7 3.8 3.9 3.5 4.2 4.9 4.1 AIR TEMPERATURE (�F) Minimum 15 10 26 36 45 56 61 66 48 37 26 18 10 01% S 41 42 47 56 65 73 75 74 70 59 49 44 58 Mean 62.9 63.7 66.3 71.4 77.1 82.1 84.0 84.0 82.3 76.8 70.3 66.0 73.9 99% S 77 76 78 83 87 90 92 93 92 89 83 78 85 Maximum 84 86 86 90 94 95 100 100 100 93 91 84 100 S 32 �F (% freq.) + + + 0.0 0.0 0.0 0.0 0.0 0.0 0.0 + + + 2 85 �F (% freq.) 0.0 + 0.1 0.4 2.7 18.5 36.0 40.0 21.1 4.5 0.3 0.0 10.3 * Galveston Channel fog signal + - less than 0.05% Table 18 Continued ENVIRONMENTAL DATA SUMMARY (PART 3) AREA: Galveston, Texas ENVIRONMENTAL FACTORS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC ANN RELATIVE HUMIDITY (%) Mean 79 80 81 82 82 80 79 78 77 74 77 78 79 SEA TEMPERATURE (�F) Minimum 48 47 49 53 66 69 73 76 74 66 56 50 47 01% S 52 52 55 62 69 76 80 80 77 70 62 57 66 Mean 66.8 66.0 67.3 71.0 77.0 82.4 84.9 85.4 84.1 80.4 74.6 70.1 75.8 99% S 78 78 76 80 83 88 90 92 89 85 82 78 83 Maximum 84 86 80 86 92 92 92 94 94 90 86 86 94 SALINITY (%o) Minimum 20.3 21.7 22.0 15.6 13.1 16.9 3.9 20.5 18.4 21.0 19.7 23.8 3.9 Mean 28.5 28.5 26.8 26.9 25.2 27.4 30.3 32.0 27.5 27.9 28.2 29.2 28.2 Maximum 33.8 34.4 31.9 31.5 33.1 34.0 37.9 38.2 34.1 32.3 33.8 33.2 38.2 DENSITY (p) Mean (at)* 15.8 15.2 15.2 15.2 14.3 14.8 18.4 22.0 20.0 18.5 18.1 17.0 17.0 SEA-LEVEL PRESSURE (mb) Minimum 996 994 996 993 1000 985 999 996 981 1000 998 1000 981 01% S 1005 1003 1002 1003 1005 1006 1009 1009 1004 1006 1005 1005 1005 Mean 1020 1018 1017 1016 1015 1015 1017 1016 1015 1017 1019 1020 1017 99% S 1034 1033 1032 1029 1026 1025 1025 1022 1024 1029 1034 1033 1028 Maximum 1040 1041 1038 1031 1031 1029 1027 1028 1025 1037 1040 1040 1041 * t (P - 1) X 103; p - gm cm-3 Table 18 Continued k Appendix A Tropical Cyclone Data Summaries 117 APPENDIX A TROPICAL CYCLONES PENETRATING THE SUB- SQUARE (SS) REGIONS OF MACHIASPORT, RARITAN BAY AND OFFSHORE SANDY HOOK, DELAWARE BAY AND OFFSHORE DELAWARE BAY, MISSISSIPPI DELTA, AND GALVESTON BAY This study considers the actual occurrence of tropical cy- clones that "penetrated" a sub-square (SS) boundary for five coastal areas of the United States. If a tropical cyclone pene- trated any of the sub-squares (SS) in any respect (passing through or skimming a corner of the sub-square), it was consid- ered a "penetration." This differs from the terminology of a "estrike zone"? in the main text which refers to a tropical cyclone moving onshore only in any of several designated coastal zones which are about 50 miles in length. Maximum tropical cyclone activity for these five sub-squares (SS) occurs in the months of August and September with the latter being the peak month. The favored season of tropical cyclone activity for the Atlantic coast is July through September. This area is not nearly as prone to intense tropical cyclone activity in June or October. Tropical cyclone activity is more intense and has a longer season along the Gulf coast. The hurricane genesis regions are the Western Caribbean and the Gulf of Mexico. The period from 118 June to early November favors tropical cyclone activity for this area. Referring to Technical Paper No. 55 (Cry), no tropical cy- clone activity existed in the Gulf of Mexico for the following years: 1876, 1883, 1884, 1890, 1927, 1952, and 1962. The chronological listing for each sub-square (SS) was ob- tained from several references. Each is preceded by a letter designating its code in the "Reference Found" column of each listing. These references are brief since their entirety may be found in the bibliography. They are: D = Dunn and Miller, Atlantic Hurricanes L = Ludlum, Early American Hurricanes 1492-1870 N = USAF, USMC, USN Annual Hurricane or Reports, 1950-1970 R = Cry, Technical Paper No. 55, Tropical Cyclones of the North Atlantic 1871-1963 T = Tannehill, Hurricanes, Chapter XV W = Mariners Weather Log, Vol. 16, No. 1, January 1972. For the period before 1871, the references relied heavily on Dunn, Ludlum and occasionally Tannehill. Technical Paper No. 55 (Cry) presented a reliable and continuous source of tropical cy- clone data (1871 to 1963) including tropical cyclone intensities (1886 to 1963). Prior to 1886 no accurate assessment of tropical cyclone intensity (wind) was available. The intensity column before 1886 remains blank for this reason. The intensity classification in- corporated into this Appendix commencing with tropical cyclones 119 in 1886 is: TS = Tropical Storm (sustained winds 34 to 63 knots) and H = Hurricane (sustained winds greater than 63 knots). In addition, a table is included listing the tropical cyclone inten- sity by month and period. Charts 1-12 at the end of this Appendix show tropical cyclone movement roses based on the period 1886-1957. 120 MACHIASPORT REGION This "penetration" study considered a sub-square (SS) bounded by 45ON68OW to 450N66.5"W on the north to 44�N68�W to 44�N66.5"W on the south. "Penetration" has to be inside the SS. After refer- ring to Technical Paper #55 (Cry) containing the general path of tropical cyclones through the study area, it was felt that any tropical cyclones prior to 1871 should have some indication of passing east of Cape Cod from the south or over Massachusetts Bay or Boston from the south or southwest in order to reach the SS. This generally appears to be the most favored cyclone track. Only the months July through September were considered. Cyclone movements in the vicinity of Nova Scotia were considered. The following tropical cyclones presented the above characteristics and probably penetrated the SS. YEAR DATE INTENSITY REF. FOUND 1635 Mid Aug. D,L 1638 23-25 Sept. D,L 1675 Late Aug. L 1727 Sept. L 1806 Late Aug. L 1830 Mid Aug. L 1839 30-31 Aug. L 1850 9-10 Sept. L 1858 Mid Sept. L 1867 3 Aug. L 1885 23 Sept. R Total: 11 Tropical Cyclones 1888 22 Aug. TS R 1888 12 Sept. TS R 121 YEAR DATE INTENSITY REF. FOUND 1888 22 Sept. TS R 1889 25 Sept. H R 1940 2 Sept. TS R 1953 7 Sept. H N,R 1954 11 Sept. H Edna N,R 1969 10 Sept. H Gerda N 1971 14 Sept. TS Heida W Total: 9 Tropical Cyclones for the period 1886 - 1971 consist- ing of 5 Tropical Storms (TS) and 4 Hurricanes (H) Period 1635 to 1971: 20 recorded Tropical Cyclones Period Aug. Sept. Total Before 1871 6 4 10 Tropical Cyclones 1871 - 1971 1 9 10 Tropical Cyclones 1886 - 1971 (1)(0) (4)(4) (5 Tropical Storms) (4 Hurricanes) 122 RARITAN BAY AND OFF SANDY HOOK REGION This "penetration" study considered a sub-square (SS) bounded by 41�N74.5*W to 41�N73�W on the north to 400N74.5�W to 40�73�W on the south. "Penetration" has to be inside the SS. Any tropical cyclones prior to 1871 were included in the listing below if the reference material indicated a passage along the middle to north- ern New Jersey coast or western Long Island. Only the months July through September were considered. Most tropical cyclones penetrating this SS originate in the Southern North Atlantic moving in a path generally westward then northerly from 250N along the Atlantic Coast. YEAR DATE INTENSITY REF. FOUND 1769 Early Sept. L 1788 19-20 Aug. D,L 1806 21-23 Aug. L 1815 22-23 Sept. D,L 1821 3 Sept. D,L 1874 29 Sept. R 1882 23 Sept. R Total: 7 Tropical Cyclones 1888 11 Sept. TS R 1893 23-24 Aug. H D,R 1897 24 Sept. TS R 1904 14 Sept. TS D,R 1944 14 Sept. H D,R 1954 31 Aug. H Carol D,R 1955 18 Aug. TS Diane D,N,R 1960 30 July TS Brenda N,R 1960 12 Sept. H Donna N,R 1961 14 Sept. TS R 1971 27-28 Aug. TS Doria W Total: 11 Tropical Cyclones for the period 1886 - 1971 consisting of 7 Tropical Storms (TS) and 4 Hurricanes (H) 123 Period 1769 to 1971: 18 recorded Tropical Cyclones Period July Aug. Sept. Total Before 1871 0 2 3 5 Tropical Cyclones 1871 - 1971 1 4 8 13 Tropical Cyclones 1886 - 1971 (1)(0) (2)(2) (4)(2) (7 Tropical Storms) (4 Hurricanes) 124 DELAWARE BAY AND OFFSHORE DELAWARE BAY This "penetration" study considered a sub-square (SS) bounded by 39.3�N75.5�W to 39.3�N74�W on the north to 38.3�N75.5�W to 38.3� N74�W on the south. "Penetration" has to be inside the SS. Any tropical cyclones prior to 1871 were included in the listing be- low if the reference material indicated a passage along the Dela- ware Bay Region or the southern New Jersey coastline. Only the months July through September were considered. Tropical cyclones penetrating this SS usually originate in the Southern North At- lantic and move in a path westward and then northward along the Atlantic coast. Some cross inland over the Carolinas and exit into this SS. YEAR DATE INTENSITY REF. FOUND 1769 Early Sept. L 1788 19-20 Aug. D,L 1806 21-23 Aug. L 1821 3 Sept. D,L 1867 Early Aug. L 1874 29 Sept. R 1881 10 Sept. R 1882 11 Sept. R 1882 23 Sept. R Total: 9 Tropical Cyclones 1888 11 Sept. TS R 1897 23 Sept. TS R 1903 16 Sept. H D,R 1904 14 Sept. TS D,R 1943 30 Sept. TS D,R 1944 2 Aug. TS R 1944 14 Sept. H D,R 1960 30 July TS Brenda N,R 125 YEAR DATE INTENSITY REF. FOUND 1960 12 Sept. H Donna N,R 1961 14 Sept. TS R 1971 27-28 Aug. TS Doria W Total: 11 Tropical Cyclones for the period 1886 - 1971 consist- ing of 8 Tropical Storms (TS) and 3 Hurricanes (H) Period 1769 to 1971: 20 recorded Tropical Cyclones Period July Aug. Sept. Total Before 1871 0 3 2 5 Tropical Cyclones 1871 - 1971 1 2 12 15 Tropical Cyclones 1886 - 1971 (1)(0) (2)(0) (5)(3) (8 Tropical Storms) (3 Hurricanes) 126 MISSISSIPPI DELTA REGION This "penetration" study considered a sub-square (SS) bounded by 300N900W and 30�N880W on the north to 280N90�W and 280N880W on the south. "Penetration" has to be inside this SS. Tropical cy- clones penetrating this SS originate in the Gulf of Mexico moving north, the Southern North Atlantic moving west (generally through the Caribbean and Yucatan Channel) or in the Caribbean moving north or northwest through the Yucatan Channel. YEAR DATE INTENSITY REF. FOUND 1711 11-13 Sept. D,T 1722 12-13 Sept. D,L,T 1740 12 Sept. D,L 1772 Sept. D,L 1778 7-10 Oct. D,L 1779 18 Aug. D,L 1780 24 Aug. D,L,T 1781 23 Aug. T 1793 Aug. D,L 1794 Late Aug. D,L 1812 19 Aug. D,L 1819 27-28 July D,L 1821 Mid Sept. D,L 1822 7-8 July D,L 1831 16-17 Aug. D,L 1837 6-7 Oct. D,L 1855 15 Sept. L 1856 10-11 Aug. D,L 1860 11 Aug. D,L 1860 15 Sept. D,L 1860 Oct. L 1871 4 Oct. R 1872 10-11 July R 1875 26 Sept. R 1877 18-19 Sept. D,R 1877 25-26 Oct. R 1878 10 Oct. R 1879 6 Oct. D,R 127 YEAR DATE INTENSITY REF. FOUND 1882 9 Sept. R 1885 29-30 Aug. R 1885 20 Sept. R 1885 25-26 Sept. D,R Total: 32 Tropical Cyclones 1887 18-19 Oct. H D,R 1889 22-23 Sept. H D,R 1892 12 Sept. TS D,R 1893 1-2 Oct. H D,R 1895 15-16 Aug. TS D,R 1897 12 Sept. H D,R 1900 12-13 Sept. TS D,R 1901 14-15 Aug. H D,R 1901 17 Sept. TS R 1902 10 Oct. TS D,R 1904 2 Nov. TS D,R 1906 26-27 Sept. H D,R 1907 21 Sept. TS D,R 1909 20-21 Sept. H D,R 1912 13-14 Sept. H D,R 1915 29 Sept. H D,R 1916 5 July H D,R 1916 18 Oct. H D,R 1917 27-28 Sept. H D,R 1923 17 Oct. TS D,R 1934 23-24 July TS R 1934 5 Oct. TS R 1936 27 July TS D,R 1937 19 Sept. TS D,R 1939 15-16 June TS D,R 1940 5 Aug. TS D,R 1941 12 Sept. TS R 1943 26 July H R 1944 10 Sept. TS D,R 1946 14-15 June TS R 1947 18-19 Sept. H D,R 1948 8 July TS D,R 1948 4 Sept. H D,R 1950 30-31 Aug. H Baker D,N,R 1953 19 Sept. TS R 1955 1 Aug. TS Brenda D,N,R 1955 26-27 Aug. TS D,R 1956 24 Sept. H Flossy D,NR 1959 7-8 Oct. TS Irene N,R 1960 15 Sept. H Ethel N,R 128 YEAR DATE INTENSITY REF. FOUND 1965 9-10 Sept. H Betsy N 1965 28 Sept. TS Debbie N 1969 17-18 Aug. H Camille N Total: 43 Tropical Cyclones for the period 1886 - 1971 consist- ing of 23 Tropical Storms (TS) and 20 Hurricanes (H) Period 1711 to 1971: 75 recorded Tropical Cyclones Period June July Aug. Sept. Before 1871 - 2 9 7 1871 - 1971 2 6 8 26 1886 - 1971 (1)(0) (3)(2) (3)(4) (10)(11) Period Oct. Nov. Total Before 1871 3 - 21 Tropical Cyclones 1871 - 1971 11 1 54 Tropical Cyclones 1886 - 1971 (5)(3) (1)(0) (23 Tropical Storms) (20 Hurricanes) 129 GALVESTON BAY REGION This "penetration" study considered a sub-square (SS) bounded on the SW by 28.5�N96�W, on the SE by 28.5�N94�W and on the north by the Texas Coast. "Penetration" has to be inside this SS. Most tropical cyclones penetrating this SS originate in the Gulf or in the Caribbean moving westward through the Yucatan Channel. During the time period 1767-1817 and 1819-1836 this Region remained un- inhabited except for Indians and Pirates. YEAR DATE INTENSITY REF. FOUND 1766 4 Sept. D,L,T 1818 12-14 Sept. D,L 1837 3-6 Oct. D,L 1839 5 Nov. D 1842 17-18 Sept. D 1854 17-18 Sept. D,L 1867 3 Oct. D,L 1871 4 June D,R 1871 9 June D,R 1877 17 Sept. D,R 1879 22-23 Aug. D,R 1880 24 June R Total: 12 Tropical Cyclones 1886 14 June TS D,R 1886 12 Oct. H D,R 1888 16-17 June H D,R 1888 5 July TS D,R 1891 4-5 July H D,R 1895 6 Oct. TS D,R 1898 27-28 Sept. TS D,R 1900 8 Sept. H D,L,R 1909 21 July H D,R 1915 16-17 Aug. H D,L,R 1932 13 Aug. H D,R 1933 22-23 July TS D,R 1934 27 Aug. TS D,R 130 YEAR DATE INTENSITY REF. FOUND 1938 17 Oct. TS D,R 1940 23 Sept. TS D,R 1941 14 Sept. TS D,R 1941 23 Sept. TS D,R 1942 20-21 Aug. H DR 1942 29-30 Aug. H D,R 1943 27 July H D,R 1945 20-21 July TS R 1947 24 Aug. H D,R 1949 3-4 Oct. H D,R 1957 27 June H Audrey D,N,R 1959 24-25 July H Debra N,R 1963 16-17 Sept. TS Cindy N,R 1964 7-8 Aug. TS Abby N 1970 16 Sept. TS Felice N 1971 10 Sept. H Fern W Total: 29 Tropical Cyclones for the period 1886 - 1971 consist- ing of 14 Tropical Storms (TS) and 15 Hurricanes (H) Period 1766 to 1971: 41 recorded Tropical Cyclones Period June July Aug. Sept. Before 1871 - - - 4 1871 - 1971 6 7 8 9 1886 - 1971 (l)(2) (3)(4) (2)(5) (5)(3) Period Oct. Nov. Total Before 1871 2 1 7 Tropical Cyclones 1871 - 1971 4 - 34 Tropical Cyclones 1886 - 1971 (2)(2) - (13 Tropical Storms) (16 Hurricanes) 131 TROPICAL STORMS & HURRICANES JANUARY 100' 90' 80, 70' 60' 50' 40' 30' 20' 50. Isrnoanqsoo ~ ~ - I I 1 50' roni edcrrr~ ... .. roca.) Sped ritd diue Uaran ensedh knot o .--cnner F Hrriane ad Tropicl St.-n Fincldi.ra 5' P, oF adc -rcsr.d irce5olciue *,-cS' .1 F -- - �--tan-ce--I F-eq...n- Noeher oF ..niansad Tropica1 S.-n,r 1886 1951. Nut: Siegis Fig-r in ersoF ros idicte th.,pmm 40' fcn40' - +++++ + + + 20' +~~~~~~~~~% 100, 9 ~ ~~~~~~~ 0' o 70' 60' 50' 40' 30' 0 TROPICAL STORMS & HURRICANES FEBRUARY 100, 9 0 O 80 70' 60, 50, 0 30e 20e 5O. Direotian Frequency, Bars represen pcrtag Iq-nc oF OMI 50, kcricaneondlro.picolenartnrone...n... Enoclrpene2D%. nZ - - (60% of all oton aod --d NE) hurican and nopi.a.tomercrnr -. lA ned -at .aS b-anne ) iknt]/ 7Ncntn,r oF Horioes- and Tropica Ston (including Seod bongtud i .S. F K Sd.b � Storm---51 Fnencnc Nualten oF 1-unnane ond Trnpi-alStn, NtSingle Gioct in cente of rol indicae th.ra freqoenn. ad nubnsroohornnton-en squat 303 ace ~~~~~~~~~~~~~~~~~~~~~~~~~~~CHART 30 20' F~ 20, 10c, 90s 8 7e 0 50' 40' 30' 20, TROPICAL STORMS & HURRICANES MARCH 100 9 0 , 80, 70' 60, 50, 40' 30' 2 - I88%ofB---., ponk ..d li.6 S,,d. -~.d~fiosmrsn,.,pik.t - ..d.b I - Slorm--- F,.qu~c .um..al1ur,,c,,.T-pkoIS,,, 886- 1957. 40'f~.codm~oosro.on.w 40' 30 , 30' + �~~~~~ 200 9 0 0 0 '6,5, 0 0 20, TROPICAL STORMS & HURRICANES APRIL I001 90, s o , 70' 80' 50, 40' 30' 20' 509 Dire-i.F,.9 .oBsers.n 9 ... .......encyof I I ho86oooe .nd E*kI~ n . ,hn Eoi, nJo 20%. --------- .-doood NE.) ------ (M- Wd fo* 14n~nlno oodi klt) o ~~--Nnn~~~bor of! fIrnoo onjroolSon inoding *---noonooooodloon~bnnnno ino...o5.oFloil by + + + 1886 1957. No.,. Si,ngl V.,.. i. mn f moindionmo, th* Prn 40' 40' -- + + .+ - + 10,~~~~~~~~~~~~~~~~~~~~~0 100' 90' s o , 70' 60' 50' 40' 30' 20' TROPICAL STORMS & HURRICANES MAY 100" 90, s o, 70' 60, 50, 40Q 30, 20, 6uicar and hnpkI.c ccesc Each cld. rpresert SOI 50oreinrrq-rvBn ersetpecnog rquny iII 0 5. e. .. IdO !dmmk.cccsdta, f ~ ~ ~ ~ 9 -necelaraeraqmaeednnta h~~~~ffi-Topca -dm' findcdhn -l~unln~rof flrricns, cd rooement ah � StrmFneusntnNotho c Kulocon ad T ropica Stno.-ldd, 1886-1957.C 30, 30'- I 1 614 10 12 + + I � � � - 1 + + 14 5 ~~~ ~ "N 128a 14 o'%'~~~~~~~~l 20,~ ~~~~~~~~~~~I ~ 100, 9 ~ ~~~~~~~0, o 70' 60' 50, 40' 30, 20, TROPICAL STORMS & HURRICANES JUNE lo0e 90, s o, 70' e0 50, 4 0 m 3 0 20' 50. we-F - . ... -I II. .. --f2 1 50. - (6O0u1ultconacmond mo,d NEI % . hurrae cd ro.pioci ctomrne, enc AI l - (Menor men.d ci ectei -nne.ht -o 14 Wiptc N.-umhe of Hutnin..ec cod Toninc Stors (incldingG~ I ~ - nnurnutres cd loupe) uhe6-d incc 'o otticb j. n c 5' cf Icgtue -Z9.tu ZNJ Z -Storm-- -nqeoNme iiuocncad Inopinl Sto-. Y ~ \zPN 1886 -1957. zro~to Note, Single figuc ic cneuf rcce indinct that ctm i 90 i c-* frequ... oycod nuber ci che-tic- unaeul 40' 2040' ___~~~~~~ ~~~~~~ ~ 8 6 13 14 9 19 10 1S 116 25 + 11 9 i0~~~~~~~~~~ ~~~~-9--- I ~~~~~~~~CHART 9 9 1I1 9 7 12 lt- 1610O 10 166 ' 20 94% Hl 32i~0o 0 10, o 100' 90' o 70' 60' 50, 40' 3 0 m 20, TROPICAL STORMS & HURRICANES JULY 100, 901 so, 70' 60' 50' 40' 30' 20' hurcicaccndfrcccclcccn .ceet Ecchcintancaant2DX 2 W-8% . . -dioccod NF) Pcocicrs ad to.-pica l ...ntcnnst. c i.k-c -Noarben ci H-nince ...n.d Tropicci Stcns(coin-3 .3 nantos acdl-psc--od in ....a5'oilotpuda by- 3'cf 24nacode. N.,.: Siogle Aigat in centr cI rose indiate that sArs 40~ ~ ~ ~~~~,- fnqsn-adnonnb~rcicisnotcnc .ceql. 1-'tv -5 30 30 4'S 40' 1025-0 -2,Z5 -5 0 ~~~~~8 +~~~~~~~~~ 20' 7 9 1 88 -4 7 14 -l >0 +� 20 8* *2l TROPICAL STORMS & HURRICANES AUGUST 100, 90' 80' 70' e0m 50, 40' 30' 20, 50' DiwooionFroooo- os.pro..t ......gof.qunyf1 ot221 2 -3 -oi 50 -itio, ood-rop-oot-o-oo.,odotE. -.... .. ..o d of . t, w otooo a 4fo, -NoAh, oF H-oiooo ...a d OTpi-o Sto1faldo 2 z 1 oeooaooiooat ~ ~ i ooloto 5oodoo'.Flloiodohy 2.0 2 1 A 24 3- 32 22W A 42 -----------a.- 1 oyNurh-ob ohoo, Fndlropi-d lTroto-t f........ ..d -ohot of ohoohaoooool 40' 6 10~0 I c27 ~~~~~~~~10~~~~~~~~~~~~~N 1315 lb 1&9 14 -4 40J \ C ct o' 0 1 3 15 8 9 1 ~~~~~~~~~9 1 3 1 1CI 13 17 16_14_ 1+11 12. 16 6 12 211 1 '2 1 31C74 4_ 13~~~~~~~~~~~~~~~~~~~~~~' 14 +,77 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~'- 7 13 1 +'~~iI I31 1 0 ++ 10' �00' 90' 80 50' 40'1430' 22' TROPICAL STORMS & HURRICANES SEPTEMBER 100, 9000 70' 60, 0 40' 30, 20' korron-ad rrop.ooi str knaamenl -z\ -) nenoralone ordbanalabseoed i arsa5%l atitue by 42 2-25- 2 15 3+ 16 -27 16 -2.8 30 16 7+23 3 +2 1666 .1957. 25" I. 6e~ 40'2 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~40' 40' 10 1 7 V7 22 '18 6 ~~~~~~~~~17 -20 6 16 -21 16 IS -22 20 -23 12 27 21 10 6 17 16 22 -1,224 14 22 -1414 15 17120 131 14+1513 17 16� 10 149 16 3123 12 I1510 +1~~~~~~~~~~~~~~~~~~~. ~ 1I4 1 ' IE"4 I a 10+1 16 16 >~ -I 0 30' 10 6 1540 11 V~~~~~~ 12 �0 12 10 12 10 1 4~ , 6,l>1 6 10 5 -- 10 9 b-o I 1 1 10121 2100 1 3 11 11- 10 13 I1, 16 11 11 I1-I 1 3 14 25 14 13 8I-1 0 5 6 6 )56 ~~~~') ~~~ 10 5 ~ ~ ~~ ~ 10 /~~~~'n~~ K~~~\ 12n)~~~~) 13 14 ~~~~~ ~ ,/~~~2 I 4!Y ~/~. CHART~ 6 6 46 I - 6 I - I SO +12$ II +14 10~ to 10 10 11I10 I1 ~~1 i ~~ g s 1 0 � 16lfI 1 is310 ,$ +- 20'~~~~~~~~~~~~~~~~~~~~~ lO \i 4j lt II 5 61 '231 '3 '6jr1 -- 6101~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~4 to 10 6 1� - a - 3 �2 1 +0 1 2 +4 +0 16 -r1 0 ~~~~~~~~0~~~ IC -~~~3 _ 9~~~~~~~~~~~~~~~7- a. 4~~~~ TROPICAL STORMS & HURRICANES OCTOBER 100, 90,0 70' 60, 50 40' 30 20, 50, ~ ~ ~ Dieto~e~ec asepe~Ip~ tog.F-q~c o 221 7Z "-22 "6-0tnI33 15 45IS1 26 361 35 27 4 0 15l 50 ~ ~~~~~~~~~~~~. . ........ ... troica tor .o t.oboolrp,.... 2O0T~thZ -WI of oi -tnn .-cd tood NE) ....oot.... ..d..p"~beodorootttdb 4 25 221-t'3 42 16 Z335V 1686 - 1957. 23 N.,.e SiogI.li- Scor - . cete idi-ote h.c,r t 40'sa 10 10 4 0 8 21 14 -22 8 22 191 7- ~ 1 2 \ - ,6 i 2 24 27 20 - + + ~~~~~~~~~~~~~~~~,4~~~~1 0 03 + + 13 15 10 25 12+0 15 isis8 4 17 ~ 3 715 14 -5 16 -16~ 20 11 16 10 14 13 15+ 12 I 7 12 3 9 1 ~ ~ ~~~~6 42 7 soc �-~~~~~~~S--"--~~~~~86 5 106 a8 9 16 16 16 8 6 4r 30 ' 6 18 I 20A 1 1�4 1 5 14 14 -.I6 17 9 ,17 12 16 -17 12 11 16 1 1- 16 13 1 2 I 4 5 1 ~~~~~~~~~~~~~~~~~~~~~~~~10 210 12 1 +6 1045 10 11 42+10 8 .,) 7 14" 5 ;36 7 17 14 121 0, -I5 15 161213 1 4 121 7 60 4 .5~ ~ ~ ~~~~~~~~ 6 " 2 1� 0 -l 3 20 2cr- 14 ~~~~~ ~~ ~~~ ~~~~ ~~~~7 14 I o 8 1410 VIa o� I I ~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~6 I0 100' 90, SO 70' 60' 50, 40' 30' 20, TROPICAL STORMS & HURRICANES NOVEMBER 100, 90, 80 70' 60, 50, 40' 30, 20, 50~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 0 - ~d 1,.,m.180 ,n0E..h 6,dlrp ,..... 20%X3 30 38 38 35 20 1 4 - - - (Moo mod of omo9ooooOoo14 6O%) -Nomborof~~~~~~~~~~onoonoo oodlnooiool~~~~~~~~~~~~~~~~~lo~~~~lilodioo 16 22 30 10 10 17~~~~~~~~~~~~~3 2 0 1 16~~~ + + --0-----H.,i.. di.obT-ono lI4\ 4-b 5 IBM 19od 40' - 1 723 ''20 '-1 9 28 9 14 8 1 7 14 -.18 20 4 0 - ~~~ ~~~~~~~~~ ~~~~14 14 - ' 12 '-1+1 '6, 10N 14 -22 - 6i 1'061\ 14 \21 1 6 168 13 13 1 9 17 8 a 14 10 I16 105 8 20 9 1 0 17 6 .9-. 9 6 6CHR 1 ~ ~~~~~~ ~~~~~~~~~~ 4 ) 8 14 -~~~~~~~~~~~l +015 1 14 1, + 816 2 + 0 2 4 I+16 14 16 16 8�+ - 2~~~~~~~~~~06 44 20 0 8 / ~K)' I 0 100, 9 0, s o, 700 600 50, 40' 30' 20' TROPICAL STORMS & HURRICANES DECEMBER 100, 90, 80, 70' 60, 50, 40' 30, 20' 50' fl-l-lo~ooooop.~o pecno -feoo7F Iz - . s I0 hv,,o~o8,r~olootomS E-nN &d 20%M 30 S05p,d.intd fi ..... ...... ....~ .p in k-ot of -N..tb., oF H-ttiot- ond Trotnool S.-rt (modina ( 1886 -1957. N-t, Sittals fig-t i. -1nte of --, i-di-loo th-1Sor 40'- 40' 30' ~~~~~~~~~~~~~~~~~~~~~ C~~~~~~~HART 12 + ~ ~~+ + � 20' 20, ~~~~~~~~~~~~~~I I I10 10' 100' 90' s o , 70' 60' 50' 40' 30' 20' Appendix B Cyclone Track Charts These charts show generalized tracks of moving cyclonic storms, both tropical and extratropical. 144 t0~~~~~~~~~~~c . 0 . r 401 STORM TRACKS JANUARY 4t0 tfrfr~~~~ ~~~ ~ 80- 70- 0 SW ' G. 30-- StF,~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CHAR LT]~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4.3 /ai i0' /R S- T- Primary frock, clang whic ther hoe bee ....... Secodery trak, along which ther h., hea maderte o to- coccrto f indiodool stor cecte paths to't0o 90- 00- 70- 6-50- 10- 30- 20- 0a- 0- '0-20 30-40 I........ STORM TRACKS FEBRUARY 4i0 lo w 9w 7 ~ 50 A0' R o 1w -,d ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ - W ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~IL w - 00.1m ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~St-r Trac.ks V. PH-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~Scnay t-ak, clang whih ther h., kbe mdeat i. . W P. P. 7. P. P. . . . P. P. P. i. P. P. 4. ..................0 Iw 90- S W 70- w 30- 20- 1,,, m I V 20'~~~~~~~~~~~~~~~~~4 STORMS TRACKSMAC 1w 50 90, 90 70' 60- wo 40- 3r 20. 50 0 4N.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 Stor Traks Primary trak, alon which share has eemairar Sacadary trak, along which her- has haa moderat to. - occrtc f irdicidoal sorm crate paths Tim D M 0 90w0 701 60w0 40' 30' 20' 50D'0 2D' 30' 0 STORM TRACKSAPI 7110' 100 90 80 70' 80w0 0 0 20' 0'0 _40' 20~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~S- -- Pyimer trak, iang which ther has bee macinteo- -~ ~~~~~~~~~~~~-1. I i-m-Ia... ......' cacnrlinc nicd tatcne paths. 110' 00 90' 80 70' 0 50' 40' 30' 20' 10' 0' 10 20' 30' 40' 4. -q 4. 1~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... STORM TRACKS MAY 1w 90-80 70- 64 54 44 34.24 4 40. 20- S- T-- 0 Primay trak, along which ther has bea- aiu t0.- Sacndey trak, along hwhih ther ha- bee moerte0. arerraiar aF indivdual st-r ceter paths. ......... ...... .. .... .... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0- tt4 70. 90. 84 74.0.-4 4 30-2.4 . aZ i STORM TRACKS JUNE tP ~ ~ ~ ~ ~ ~~~~~~ge Stor Traks Primary trak, al -on which tkcto has kna crocinco - . *..''~~" corooctrotion of indvdualtor carter paths. low too0so so, 7. so SW. 4o. 3o. a o. to. D . to. so. so to. STORM TRACKS JULY Ito 9 00' Wo 0 70- o 50- 401 0 0 to. 0 0 St-r Traks Nome -N~~~~~~~~~~~~~~~~~~~~~~~al. - ~~~~~~~~~~~~~~~Primary trak, eing which ther h., heat maximum --conc-nra-ien e individual ttt etrpaths. S-cadary trak, alan which ther has been madarte o tI0' tOO' 90' W 0 W 0 W 0 A M '40 3' 2.0' to. 0'to 20- 30' 40' STORM TRACKS AUGUST -&~~~~~~~~~~~~~~ - 20-~~~~~~~~~~~~~~~~~~~~~~- w ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~w. Fidd. - -pi "t, Primard.y track, oloag which those hoc boor moa-tm law - o - Soonor track a3on whic thor has has modarato STORM TRACKS SEPTEMBER 110. 100' 90, 0 701 0 5'w4 3(r 20- 10' 0 X-~~~~~~~~~~~~~~~~~~~~~~~-0 ',d~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 6D-~ ~ ~ ~ ~ ~ ~ ~~ ~ ~ ~ ~~~~~~~~~~~~~~~~~~~~~~~~~ rmr ok iogwihteehehe aio - -. - 40' 20' a"~~~~~ coocentr~~~rion ii ?d~CHl trcAnR pths cn~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ermdrr to. ~~~~~-700 3, ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~~~~~~0 0 10, ~~~~~~~~~~~~~40- STORM TRACKS OCTOBER ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~S- 106 Cal - SW~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~al ll o-\ 0 Stor Track2.10 1- wSW a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 1-..... STORM TRACKS NOVEMBER 163' 93' 63'~ 70' 63 W3 40W3 20. l o- 3'( ~~~~~~~~~~~~~CAR 33'-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~,d. a- -r, m ........ . ... .. .... .. .. jw W 70- W 50, A & 2 & I & 0. lo- 2w 3D' 40-~~~~~~~~~~~~~~~~~~~~~~~~~~~~StrmTrck t0~ ~~~~ . 0 S. . 40... STORM TRACKS DECEMBER too- w w7D. O. . ... lO. 50. 40, 3 O' 0t /~~~~~~~~C 4W~~~~~~~~~~~~ w Stor Troks -701"N ~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~pnimoy trcaogwhih thec h., been mai-ion ...........e,." ocnrto Fidvda tr cete paths. Secodary tok, along which thana. has 6ean modart tO.- * ocnrto Fidicdl str-cne paths. ......... ...... ......... .......~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~O ttO. ISO. SO. 40- 30- D - SO1O0O.S.t. OP tO. wO O 4O. /IO 420 . 4" LOW PRESSURE CENTERS DEC - JAN - FEB 110S ~ ~ tOP OP 80 0' 60 0' O. 40' P 20P IT 0 3' at -~~~~l 40'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~0 � B,,,,,p,,,,I p,, NoFaq~yyy p~,I,,,, O. ffi., .-d ~ ~ ~ I3'- ...h ~ d by ~d 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~------ f 23 Nyird 80, . d .1 ,,,,. 01 I .., 0 0 ~ ~ ~ ~ ~~~~~~i. di-i.,,~ ~~~~~~~~~~J~~~~~~~~~~~~~~~~~~~E ..r~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I --i. h 5. . P' r a~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ lip lOP 93' 00' 73' 63' 53' 43' OP OP P 3' b 1F' 23'd f . . . .. ~~~~~~~~~~~~~~~88~~-. .- 5 l- ~WF.h .h .,-i. . ...I..... ......... ........0 ]I c6 I O-6 w O o-3 0 LOW PRESSURE CENTERS MAR - APR - MAY It. oo Wo so. 70- 60, so 401 3 o 01 to, 7w AIW-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 50- - so.~~MI 1911L~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~trla ra !aylarr~.whrwic r.wyh ____ 60.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ra ir.aaar~i arwr aantrd 17~~~~~~~~~~~~~~~~~astrtalarrra.Ca~raai~ignyarih oo~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~jrdwa.ahhptilda ~r 4har 5,..ard, Prad-Oar rrd afrah ba.,para hr-ah m or.. I io. -to -Earararrdwirdladitarirhrrrvlr.ahaa 6.J 2'- la dd. fBrraa-td Fhrr ratht ar22a Ito ~ .2 o. 70' W 02 40- 3o. 2o t. . to. oo. 3oD-o. 2 r 10 20w 30 I LOW PRESSURE CENTERS JUNE - JULY - AUG 0' Vi I 90 so 70w 50. 40- 30 2w l o - ... .... .. . 2y. - 22% yE I, ... 4h..,o , -, yo~~~~~~~~~~~~~~~~~~S,..dF P6-dfto..... .r..doF ...h bo,.psot. ~o.......h Ji .,)F I,.ot,~oo ,~ . iodooddi,.oo.d (0'- ~-oo.ddodooio~qeoIVsto oIop..o, o~...... oboy-d o.o IV.1 1.ihod. h, IWo)boit R.,. oodO.d oh.. -b,,~,.,o 25 y, - .... IoV: .... I ........ ..... ......... .........~~~~~~~~~~~~~~~~~~o,,..,lIo, p,~y~oootv ndWo~iy,,ilyro,,kN2, ,oyooyodo.d,.iol 110. 09'00'0 70' w0 0 40' lo' 20 10o0-0 20' 3D' 4'I LOW PRESSURE CENTERS SEPT - OCT -NOV 100 90J 70- 4f r0 AO- 1f AO- ~~~~~~~~I-pI- 5ff~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~- b-I..24h. lo'.f ~ ~ ~ ~ ree~eoooloe N- oooeo ofbo, neeod Ceieeo- .ioooo dooio dedieobo.M 30h ..bpenisledoll.eo....241di. ...~~~~~~~~~~~~~~~hdo ooeo S' ooco esoo. ..e....of... peoos 110. 7W AG- 2D- 10. 0- ID- 2, AO-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~onl~tbsnoeh~obdeEs Eoohfeooel% BIBLIOGRAPHY 1. Commerce, Dept. of, Coast and Geodetic Survey: "Density of Sea Water at Coast and Geodetic Survey Tide Stations, Atlantic and Gulf Coasts," DW-1 Revised, 1949. 2. Commerce, Dept. of, Coast and Geodetic Survey: "Surface Water Temperature and Salinity, Atlantic Coast, North and South America," C&GS Pub. 31-1 Second Edition, 1965. 3. 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