[Federal Register Volume 60, Number 239 (Wednesday, December 13, 1995)]
[Notices]
[Pages 64020-64028]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-30246]



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DEPARTMENT OF COMMERCE

National Weather Service; Automated Surface Observing System

SUBJECT: Notice of Intent.

SUMMARY: The National Weather Service (NWS) implemented the 
Supplemental Data Program effective October 1, 1995. This program 
supplements data provided by the Automated Surface Observing System 
(ASOS). Observations produced through the Supplementary Data Program 
are transmitted separately from the ASOS operations and provide data to 
support hydrometeorological operations and climatological applications. 
This notice explains the reasons for the shift in reporting methods and 
describes how to obtain and interpret hydrometeorological information 
that was previously available in the surface aviation observation (SAO) 
format.

EFFECTIVE DATE: October 1, 1995.

ADDRESSES: Requests for information should be sent to Steve Pritchett, 
NWS, Office of Systems Operations, 1325 East-West Highway, Silver 
Spring, MD 20910 or through electronic mail at suppdata 
@smtpgate.ssmc.noaa.gov.

FOR FURTHER INFORMATION CONTACT:
Steve Pritchett at 301-713-1792.

SUPPLEMENTARY INFORMATION: As part of the NWS modernization, the NWS is 
undergoing a major shift in the methods used to observe and report 
surface weather information.
    The NWS has developed and is installing ASOS to automate certain 
observing functions, thereby taking advantage of advances in sensor and 
microprocessor technology. At approximately 900 airports in the United 
States during the 1990s, the U.S. Departments of Commerce, 
Transportation, and Defense are deploying ASOS to support aviation 
operations and weather forecasting and warnings, as well as general 
needs of the hydrometeorological, climatological, and meteorological 
research communities.
    ASOS will provide greatly expanded coverage (locations and 
observing hours), objective observations, a continuous weather watch, 
and improved operating efficiency. ASOS, when integrated with advances 
in remote sensing and weather information processing systems, is 
expected to contribute to improved warning and forecast services. ASOS 
will perform the basic observing functions necessary to generate a SAO. 
However, because some weather parameters observed manually today will 
not initially be observed by ASOS, the NWS is introducing two new 
classes of observations to the array of meteorological surface 
observations: the supplementary data observation (SDO) and the 
supplementary climate data (SCD).
    Supplementary observations are not appended to the ASOS 
observation; rather, they are disseminated as separate messages. The 
NWS will disseminate these reports to a variety of Federal and non-
Federal users of NWS data. Supplementary data will be made available 
through NWS communication systems such as Family of Services, NOAA 
Weather Wire, and various computer and commercial vendor services.
    Surface observational data in the ASOS era will continue to come 
from many sources. ASOS, along with complementary data derived from 
remote sensing technologies, such as statellites, will form the 
backbone of the surface observing network (SAO) system. Surface data 
from over 20,000 automatic and manual hydrometerological sites, 
including cooperative and hydrologic networks, will continue to play an 
important role in NWS operational forecast programs. They comprise the 
climatological data bases and supply information to users who currently 
rely on surface observations from airports, as well as for non-aviation 
related information.
    The NWS Weather Forecast Offices (WFOs) will issue these new 
supplemtary data reports. The SDOs will provide significant, event-
driven observations primarily intended to support weather forecasting 
and general hydrometeorological needs. Elements may be reported in SDOs 
on an ``as-observed'' basis and do not imply a continuous or basic 
weather watch. SDOs will not generally include elements that are in 
augmented ASOS observations from that location.
    The SCD reports may provide routinely scheduled observations useful 
for climatological applications, as well as hydrometeorological 
operations. SCDs are routinely issued at designated hours at about the 
same time as the recorded surface observation (note: the SDOs are 
issued on an event basis, which may fall ``on the hour'' only by 
chance).
    Most offices issuing SCDs and SDOs will not issue the full suite of 
SCD/SDO elements. There will be some variation among individual offices 
in the elements they report. Elements reported in SCDs will generally 
not be reported in SDOs. Exceptions are: (1) precipitation type and 
intensity reported in SCDs may also be reported in SDOs when considered 
significant by the on-site observer, and (2) volcanic ash reported in 
SCDs will also be reported in SDOs. Observations of volcanic eruptions 
and volcanic ash when first noted and severe weather (severe 
thunderstorms and tornadic 

[[Page 64021]]
activity) when first observed may be included in weather warnings and 
statements issued by cognizant NWS offices rather than in supplementary 
data reports. The same elements may be reported in both SDO's and 
aviation observations from some sites (see enclosures).
    In the future, non-Federal observers (volunteers, Cooperative 
Observers, etc.) are expected to participate as members of the 
supplementary data network. Their reports will focus on snow depth, 
snowfall amount, hail and ice pellet occurrences. It is expected that a 
subset of volunteer observers will report water equivalent of snow on 
the ground.
Susan F. Zevin,
Deputy Assistant Administrator for Operations.

Report Format and Content

    The information in supplementary data reports will follow the 
syntax and abbreviations used in Federal Meteorological Handbook Number 
1 for Surface Observations (FMH-1). (FMH-2 for synoptic cloud reports) 
where practical. Supplementary data reports differ from surface 
aviation observations in the following ways:
     Only a limited set of observed elements is included in 
supplementary data reports. A given supplementary report may contain 
one or several elements.
     Supplementary data reports are not issued on an hourly 
basis. Time-scheduled SCDs are issued at main synoptic hours or at 
other designated hours of the day depending on the variable(s) being 
reported. Event-driven SDOs are issued when a significant phenomenon is 
first observed. A follow-up ``termination'' SDO will be issued after 
the cessation of certain events.
     Some SDOs will contain a ``/'', solidus remarks separator. 
The purpose of the remarks separator is to help computer decoders 
differentiate between decodable (parsable) remarks and remarks not 
readily amendable to decoding. SCDs will not inclde the ``/'' remarks 
separator because all remarks in SCDs are decodable.
    Supplementary data reports are encoded as follows:
    SID--TYPE--(COR--)TIME--WX/--Decodable RMKS--/--Other RMKS (``--'' 
indicates a required space and ``/'' indicates a required solidus. The 
``/'' will appear in an observation if and only if one or more ``WX'' 
elements are reported and are followed by remarks. The ``/'' remarks 
separator will appear in an SDO, only if, the SDO contains both 
decodable and noncodable remarks.

SID--Station identifier (3 to 5 alphanumeric characters).
TYPE--Type of observation (either SCD or SDO). If the observation is a 
correction to a previously disseminated SCD or SDO, the contraction COR 
will follow the type of observation (in which case the time (TIME) will 
be the time of the observation being corrected).
TIME--Time of observation in hours and minutes UTC [0000 * * * 2359].
WX--Weather and/or obstructions to vision. This field will be from 1 to 
15 characters in length including the precipitation intensity symbol 
(-,+). The elements to be reported in the ``WX'' field are given in 
Table 1 of this guide. Contractions for precipitation types are given 
in Table 2; contractions for obstructions to vision are in Table 3.

    Decodable RMKS, Other RMKS--Remarks are separated from the ``WX'' 
group with a solidus and a space. If no ``WX'' is reported, the remarks 
are preceded with a space after the time (TIME) element.
    SCD remarks are encoded in the following order:

8NNhCLhCMCH--Total cloud cover and synoptic cloud 
types
931nnn--Depth of new snow (snowfall)
933RRR--Water equivalent of snow on the ground
4/sss--Depth of snow on ground
98xxx--Duration of sunshine
7R24R24R24R24--Calendar day total precipitation 
(from designated sites)
4snTxTxTxsnTnTnTn--Calendar day 
maximum and minimum temperature (from designated sites)
NIL--Nothing to report

    SDO remarks are encoded in the following order:
Temination reports for ``WX'' elements (e.g., END IP)
SNOINCR x/x--Snow increasing rapidly
HLSTO x--Size of largest hailstone observed
`` / '' remarks separator

    Other SDO remarks when considered significant by the on-site staff:

Local variation in visibility (e.g., VSBY N2; F BANK N-E2) (designated 
stations)
Virga--Precipitation evaporating before reaching ground (designated 
stations)
Precipitation not at station (e.g., RWU SW; SU OVR MTNS N) (designated 
stations)
Clouds above 12,000 feet (types and/or layers) (designated stations)
Distant clouds obscuring mountains (designated stations)
Other meteorological information considered significant, such as 
blowing volcanic ash

    The SDO ``WX'' group, remarks of snow increasing rapidly (SNOINCR), 
hailstorms (HLSTO), and termination reports for ``WX'' elements are 
considered decodable.
    Initiation and termination reports will be issued for selected 
``WX'' elements (those listed in Table 2 of this guide). An exception 
is hail, for which only an initiation report will be issued. 
Termination reports will be issued for any weather and/or obstructions 
to vision previously reported in the ``WX'' field of an SDO when the 
event is determined to have ended. Termination reports are not required 
for information reported in SDO remarks unless designated by NWS 
regional headquarters.
     The initiation report for a ``WX'' element is implicit in 
the ``WX'' field (e.g., ``MCI SDO 1325 BS'' is an initiation report for 
blowing snow). The initiation report for other significant events 
carries the information in the SDO remarks section (e.g., ``MCI SDO 
1325 BD/ RWU SW'' may be an initiation report for distant rain showers. 
The blowing dust, previously reported, continues).
     Termination reports contain the key word ``END'' followed 
by a space and a description of the event which ended. All termination 
information, even for a ``WX'' element, is considered to be in the 
remarks category. Termination information for ``WX'' elements precedes 
any `` / '' remarks separator (e.g., ``MCI SDO 1445 END BD / END RWU 
SW'').
     Termination reports for items listed under ``other SDO 
remarks when considered significant by the on-site staff'' can have 
several meanings: (1) the event ended, (2) the event is no longer 
considered significant, but it may still exist, or (3) because of 
darkness, it is not possible to determine if the event still exists.
    Plain language remarks may at times be necessary to clarify 
changing local conditions. For example, if a fog bank previously 
reported to the north (e.g., ``ANC SDO 1205 F BANK N2'') moves over the 
airport, ``ANC SDO 1330 F BANK MOVD OVR ARPT'' might be subsequently 
reported.
    Location of phenomena within 10 miles of the station will be 
reported as ``VCNTY STN,'' followed by the direction from the station. 
Phenomena between 10 and 30 miles of the station will be located by 
direction from the station. Phenomena beyond 30 miles will be reported 
as ``DSNT,'' followed by the direction from the station.
    If there are no coded remarks or weather to report in a scheduled 
SCD, 

[[Page 64022]]
the SCD will be transmitted with ``NIL'' (e.g., ``PHL SC 1758 NIL'').
    Table 1 gives the type of supplementary information reported, the 
category of the supplementary data report, criteria for reporting, and 
type of site making the report. It also gives the syntax of the element 
and one or more examples. Examples of complete supplementary data 
reports are given in the back of this guide. Except where explicitly 
stated otherwise, the ``WFO'' column refers to all WFOs, whether or not 
they have a collocated ASOS. The ``Other NWS Office'' column refers to 
NWS staffed or manual observing sites with responsibility for 
supplementary data reporting. This table represents the initial 
supplementary data reporting configuration by office type (augmented 
elements are excluded).
      

                                            Table 1.--Description of Elements Reported as Supplementary Data                                            
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                             Type of report                                              Reported by                                    
            Element             ----------------------------------------   When reported   --------------------------------------    Format, example,   
                                         SDO                 SCD                                   WFO         Other NWS offices         comments       
--------------------------------------------------------------------------------------------------------------------------------------------------------
WX--Weather and/or obstructions  ..................  X.................  at 6-hrly          X................  Designated         Format: Table 2 gives 
 to vision.                                          Volcanic ash will    synoptic times                        Stations.          contractions for     
--All precipitation types and                         not be included     (00, 06, 12, and                                         precipitation types; 
 intensities.                                         in SCDs from        18 UTC) and                                              Table 3 gives        
--Volcanic ash.................                       sites with a        staff is                                                 contractions for     
                                                      collocated ASOS.    available.                                               obstructions to      
                                                                                                                                   vision.              
                                                                                                                                  Where: ``WX'' refers  
                                                                                                                                   to weather and       
                                                                                                                                   obstructions to      
                                                                                                                                   vision. Weather      
                                                                                                                                   refers to            
                                                                                                                                   precipitation and    
                                                                                                                                   tornadoes.           
                                                                                                                                   Obstructions to      
                                                                                                                                   vision refer to      
                                                                                                                                   phenomena that reduce
                                                                                                                                   visibility but are   
                                                                                                                                   not precipitation.   
                                                                                                                                   Weather and          
                                                                                                                                   obstruction to vision
                                                                                                                                   elements included in 
                                                                                                                                   SCDs and SDOs are    
                                                                                                                                   given in the         
                                                                                                                                   ``Element'' column to
                                                                                                                                   the left.            
                                                                                                                                  Examples: VOLCANIC    
                                                                                                                                   ASH; IF; HLSTO \1/4\;
                                                                                                                                   IP-: END VOLCANIC    
                                                                                                                                   ASH; END IF          
                                                                                                                                  Comments: Visibility  
                                                                                                                                   specified by FMH-1   
                                                                                                                                   for qualifying       
                                                                                                                                   intensity of snow and
                                                                                                                                   drizzle may not be   
                                                                                                                                   well resolved at     
                                                                                                                                   certain WFOs without 
                                                                                                                                   a collocated ASOS.   
                                                                                                                                   Consequently, snow   
                                                                                                                                   and drizzle          
                                                                                                                                   intensities reported 
                                                                                                                                   by non-ASOS WFOs must
                                                                                                                                   be considered to be  
                                                                                                                                   estimates. A follow- 
                                                                                                                                   up ``termination''   
                                                                                                                                   SDO will be issued   
                                                                                                                                   upon termination of  
                                                                                                                                   the event (with the  
                                                                                                                                   exception of hail).  
                                                                                                                                   The termination SDO  
                                                                                                                                   will give the event  
                                                                                                                                   preceded by the key  
                                                                                                                                   world ``END.''       
                                                                                                                                  Volcanic ash will not 
                                                                                                                                   be reported in       
                                                                                                                                   supplementary data   
                                                                                                                                   originating from     
                                                                                                                                   sites which have     
                                                                                                                                   collocated ASOS.     
                                                                                                                                   Volcanic ash is      
                                                                                                                                   appended directly to 
                                                                                                                                   the ASOS observations
                                                                                                                                   at those sites.      
                                                                                                                                  Visibility will not be
                                                                                                                                   a factor in reporting
                                                                                                                                   ``VOLCANIC ASH'' as  
                                                                                                                                   present weather (WX) 
                                                                                                                                   in an SDO. Any       
                                                                                                                                   observed ``VOLCANIC  
                                                                                                                                   ASH'' will be        
                                                                                                                                   reported.            

[[Page 64023]]
                                                                                                                                                        
WX--Weather and/or obstructions  X.................  ..................  when observed and  X................  Designated         ......................
 to vision.                      Volcanic ash will                        staff is                              stations.                               
--Ice pellets..................   not be included                         available.                                                                    
--Volcanic ash.................   in SDOs from                                                                                                          
--Other nonaugmented elements     sites with a                                                                                                          
 when considered significant by   collocated ASOS.                                                                                                      
 the on-site staff (ice                                                                                                                                 
 crystals, ice fog, smoke,                                                                                                                              
 blowing snow, blowing sand,                                                                                                                            
 blowing dust, and blowing                                                                                                                              
 spray).                                                                                                                                                
Daily total sunshine duration..  ..................  X.................  Once daily at 08   Reported at        .................  Format: 98xxx.        
                                                                          UTC. If the        official NWS                         Where: ``98'' is the  
                                                                          station is         sunshine-                             code group indicator 
                                                                          closed at 08       duration                              and ``xxx'' gives the
                                                                          UTC, the           reporting sites.                      total minutes of     
                                                                          ``98xxx'' group    These sites may                       sunshine for the     
                                                                          will be reported   be moved as                           previous calendar    
                                                                          in the first 6-    required.                             day. ``xxx'' is      
                                                                          hrly observation                                         encoded in hundreds, 
                                                                          after opening.                                           tens, and units.     
                                                                          Equipment must                                          Example: 98096; 98000.
                                                                          be available.                                           Interpretation: 96    
                                                                                                                                   minutes of sunshine; 
                                                                                                                                   0 minutes of         
                                                                                                                                   sunshine.            
                                                                                                                                  Missing data          
                                                                                                                                   indicator: 98///.    
Calendar day total prescription  ..................  X.................  24-hour value      Only reported by   .................  Format: 7R24R24R24R24.
 accumulation (water                                                      once daily at 00   WFOs which do                        Where: ``7'' is the   
 equivalent).                                                             LST and staff is   not have a                            code group indicator;
                                                                          available.         collocated ASOS.                      R24R24R24R24 gives   
                                                                                                                                   precipitation amount 
                                                                                                                                   encoded in tens,     
                                                                                                                                   units, tenths, and   
                                                                                                                                   hundredths of inches.
                                                                                                                                  Example: 70125.       
                                                                                                                                  Interpretation: 1.25  
                                                                                                                                   inches of            
                                                                                                                                   precipitation (water 
                                                                                                                                   equivalent) in the   
                                                                                                                                   preceding 24 hours.  
                                                                                                                                  Missing data          
                                                                                                                                   indicator: 7////.    
                                                                                                                                  Comment: Note that in 
                                                                                                                                   the SCD the ``7''    
                                                                                                                                   group refers to a 24-
                                                                                                                                   hr precip total      
                                                                                                                                   ending at midnight   
                                                                                                                                   LST whereas the ``7''
                                                                                                                                   group in the remarks 
                                                                                                                                   of an ASOS           
                                                                                                                                   observation or a     
                                                                                                                                   manual surface       
                                                                                                                                   observation refers to
                                                                                                                                   a 24-hr precip total 
                                                                                                                                   ending at 12 UTC.    
Calendar day maximum and         ..................  X.................  24-hour value      Only reported by   .................  Format:               
 minimum temperatures.                                                    once daily at 00   WFOs which do                         4s,TxTxTxsnTnTnTn.   
                                                                          LST and staff is   not have a                           Where: ``4'' is the   
                                                                          available.         collocated ASOS.                      code group indicator;
                                                                                                                                   sn gives sign of the 
                                                                                                                                   data (``1'' for      
                                                                                                                                   temperatures below 0 
                                                                                                                                   deg.F, ``0'' for     
                                                                                                                                   temperatures 0 deg.F 
                                                                                                                                   or higher); TxTxTx is
                                                                                                                                   the maximum          
                                                                                                                                   temperature in whole 
                                                                                                                                   degrees F; TnTnTn is 
                                                                                                                                   the minimum          
                                                                                                                                   temperature in whole 
                                                                                                                                   degrees F.           
                                                                                                                                  Example: 400700045.   
                                                                                                                                  Interpretation: 24-hr 
                                                                                                                                   max temperature of 70
                                                                                                                                   deg.F, 24-hr min     
                                                                                                                                   temperature of 45    
                                                                                                                                   deg.F.               
                                                                                                                                  Missing data          
                                                                                                                                   indicator: 4////////.

[[Page 64024]]
                                                                                                                                                        
Snow increasing rapidly........  X.................  X.................  Hourly when snow   Designated         Designated         Format: SNOINCR x/x.  
                                                                          depth increase     stations.          stations.         Reference: FMH-1 Table
                                                                          equals or                                                A3-88, 2.e modified  
                                                                          exceeds 0.5''/hr                                         to exclude the depth 
                                                                          and staff is                                             increase since the   
                                                                          available.                                               last 6-hrly report.  
                                                                                                                                  Where: ``SNOINCR'' is 
                                                                                                                                   the code group       
                                                                                                                                   indicator. ``x/x''   
                                                                                                                                   gives the snow depth 
                                                                                                                                   increase in the past 
                                                                                                                                   hour/total depth of  
                                                                                                                                   snow on the ground at
                                                                                                                                   time of observation, 
                                                                                                                                   both of which are    
                                                                                                                                   reported in whole    
                                                                                                                                   inches.              
                                                                                                                                  Example: SNOINCR 1/6. 
                                                                                                                                  Interpretation: One   
                                                                                                                                   inch depth increase  
                                                                                                                                   in the past hour with
                                                                                                                                   6 inches on the      
                                                                                                                                   ground at time of    
                                                                                                                                   observation.         
Size of largest hailstone        X.................  ..................  when first         Designated         Designated         Format: HLSTOx.       
 observed.                                                                observed and       stations.          stations.         Where: ``HLSTO'' is   
                                                                          staff is                                                 the group indicator. 
                                                                          available.                                               ``x'' gives the      
                                                                                                                                   diameter (in inches) 
                                                                                                                                   of the largest       
                                                                                                                                   hailstone observed.  
                                                                                                                                   Hailstone size is    
                                                                                                                                   reported in \1/4\    
                                                                                                                                   inch increments. If  
                                                                                                                                   the hailstone size is
                                                                                                                                   less than \1/8\ inch,
                                                                                                                                   it will be encoded as
                                                                                                                                   <\1/4\.              
                                                                                                                                  Example: HLSTO \1/2\. 
                                                                                                                                  Interpretation: The   
                                                                                                                                   largest hailstone    
                                                                                                                                   observed was \1/2\'' 
                                                                                                                                   in diameter.         
                                                                                                                                                        
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Other Significant Weather Information                                                         
                                                                                                                                                        
--------------------------------------------------------------------------------------------------------------------------------------------------------
Significant local variations in  X.................  ..................  when observed and  Reported at        .................  Format: Description   
 visibility.                                                              staff is           specific,                             and direction from   
                                                                          available.         currently                             station.             
                                                                                             staffed NWS                          Examples: VSBY N2; F  
                                                                                             observing sites                       Bank N-E2.           
                                                                                             which are                            Interpretation: (1)   
                                                                                             determined to be                      Visability to the    
                                                                                             especially                            north is 2 miles. (2)
                                                                                             problematic with                      A fog bank exists    
                                                                                             respect to                            north through east.  
                                                                                             terrain, and                         Comment: Once         
                                                                                             multiple                              reported, significant
                                                                                             visibility                            changes to ``local   
                                                                                             sensors are not                       variations in        
                                                                                             available or do                       visibility'' will be 
                                                                                             not suffice.                          reported in updated  
                                                                                                                                   SDO reports.         
Virga..........................  X.................  ..................  when observed and  Reported at        .................  Format: ``VIRGA'' and 
                                                                          staff is           specific,                             direction from       
                                                                          available..        currently                             station.             
                                                                                             staffed NWS                          Example: VIRGA NW.    
                                                                                             observing sites                      Comment: Once         
                                                                                             in mountainous                        reported, significant
                                                                                             areas lacking                         changes to ``virga'' 
                                                                                             radar coverage                        will be reported in  
                                                                                             which are                             updated SDO reports, 
                                                                                             determined to be                      e.g., VIRGA VCNTY STN
                                                                                             especially                            NW MOVG E.           
                                                                                             problematic with                                           
                                                                                             respect to                                                 
                                                                                             terrain.                                                   

[[Page 64025]]
                                                                                                                                                        
Precipitation not at the         X.................  ..................  when observed and  Reported at        .................  Format: Type and      
 station.                                                                 staff is           specific,                             intensity (or ``U''  
                                                                          available.         currently                             if unknown) of       
                                                                                             staffed NWS                           precipitation and    
                                                                                             observing sites                       direction from       
                                                                                             in mountainous                        station.             
                                                                                             areas lacking                        Examples: RWU SW; SU  
                                                                                             radar coverage                        OVR MTNS N.          
                                                                                             which are                            Comment: Once         
                                                                                             determined to be                      reported, significant
                                                                                             especially                            changes to           
                                                                                             problematic with                      ``precipitation not  
                                                                                             respect to                            at the station'' will
                                                                                             terrain.                              be reported in       
                                                                                                                                   updated SDO reports, 
                                                                                                                                   e.g., RWU VCNTY STN  
                                                                                                                                   SW MOVD NW.          
Significant clouds above 12,000  X.................  ..................  When observed and  Reported at        .................  Format: ``CLD LYR''   
 feet AGL and significant cloud                                           staff is           specific,                             followed by one or   
 types.                                                                   available.         currently                             more cloud base      
                                                                                             staffed NWS                           heights (generally   
                                                                                             observing sites                       estimated, hundreds  
                                                                                             in mountainous                        of feet AGL) and     
                                                                                             areas which are                       amounts (SCT, BKN, or
                                                                                             determined to be                      OVC). Ceiling        
                                                                                             especially                            designators (``E''   
                                                                                             problematic with                      and ``M'') are not   
                                                                                             respect to                            reported as this     
                                                                                             terrain.                              layer may not be the 
                                                                                                                                   layer constituting a 
                                                                                                                                   ceiling. Only        
                                                                                                                                   significant cloud    
                                                                                                                                   layers above 12,000  
                                                                                                                                   feet AGL are         
                                                                                                                                   reported. Types of   
                                                                                                                                   significant clouds   
                                                                                                                                   associated with      
                                                                                                                                   orographic features, 
                                                                                                                                   such as ACSL and     
                                                                                                                                   rotor clouds, may    
                                                                                                                                   also be reported.    
                                                                                                                                  Example: CLD LYR 140  
                                                                                                                                   OVC; ACSL VCNTY STN  
                                                                                                                                   SW-W                 
                                                                                                                                  Interpretation: A     
                                                                                                                                   significant overcast 
                                                                                                                                   cloud layer based at 
                                                                                                                                   14,000 feet above    
                                                                                                                                   ground level was     
                                                                                                                                   observed.            
                                                                                                                                  Comment: Once         
                                                                                                                                   reported, significant
                                                                                                                                   changes to ``cloud   
                                                                                                                                   layers above 12,000  
                                                                                                                                   feet'' and           
                                                                                                                                   ``significant cloud  
                                                                                                                                   types'' will be      
                                                                                                                                   reported in updated  
                                                                                                                                   SDO reports, e.g., CB
                                                                                                                                   W MOVD N.            
Significant distant clouds       X.................  ..................  When observed and  Reported at        .................  Format: Description   
 obscuring mountains.                                                     staff is           specific,                             and direction from   
                                                                          available.         currently                             station.             
                                                                                             staffed NWS                          Example: CLD BASES    
                                                                                             observing sites                       OBSCG MTNS W.        
                                                                                             which are                            Interpretation: Cloud 
                                                                                             determined to be                      bases obscuring      
                                                                                             especially                            mountains to the     
                                                                                             problematic with                      west.                
                                                                                             respect to                           Comment: Once         
                                                                                             terrain.                              reported, significant
                                                                                                                                   changes to ``distant 
                                                                                                                                   clouds obscuring     
                                                                                                                                   mountains'' will be  
                                                                                                                                   reported in updated  
                                                                                                                                   SDO reports.         
Any other meteorological         X.................  ..................  When observed and  X................  X................  Format: Plain language
 information when considered                                              staff is                                                 using FMH-1          
 significant by the on-site                                               available.                                               contractions where   
 staff.                                                                                                                            practical.           
                                                                                                                                  Comments: Any         
                                                                                                                                   significant weather  
                                                                                                                                   information such as  
                                                                                                                                   convective cloud     
                                                                                                                                   types not covered    
                                                                                                                                   above may be entered 
                                                                                                                                   here if not included 
                                                                                                                                   in an ASOS           
                                                                                                                                   observation.         

[[Page 64026]]
                                                                                                                                                        
Depth of new snow..............  ..................  X.................  At 6-hrly          Designated         Designated         Format: 931nnn.       
                                                                          synoptic times     stations.          stations.         Where: ``931'' is the 
                                                                          (00, 06, 12, and                                         code group indicator 
                                                                          18 UTC) when any                                         for the amount of    
                                                                          amount of snow                                           solid precipitation  
                                                                          has fallen in                                            (i.e., snow, snow    
                                                                          the past 6 hours                                         pellets, snow grains,
                                                                          and staff is                                             ice pellets, ice     
                                                                          available.                                               crystals, and hail)  
                                                                                                                                   that fell in the past
                                                                                                                                   6 hours, even if some
                                                                                                                                   or all of it melted. 
                                                                                                                                   ``nnn'' gives the    
                                                                                                                                   depth in the frozen  
                                                                                                                                   state to the nearest 
                                                                                                                                   tenth of an inch     
                                                                                                                                   using a leading zero 
                                                                                                                                   if less than 1 inch. 
                                                                                                                                   Trace amounts are    
                                                                                                                                   reported as 931000.  
                                                                                                                                  Example: 931012.      
                                                                                                                                  Interpretation: 1.2   
                                                                                                                                   inches of new snow   
                                                                                                                                   fell in the past 6   
                                                                                                                                   hours.               
                                                                                                                                  Missing data          
                                                                                                                                   indicator: The group 
                                                                                                                                   is not reported if no
                                                                                                                                   solid precipitation  
                                                                                                                                   fell during the past 
                                                                                                                                   6 hours or if hail   
                                                                                                                                   was the only form of 
                                                                                                                                   solid precipitation. 
Water equivalent of snow on the  ..................  X.................  Once daily at 18   Designated         Designated         Format: 933RRR.       
 ground.                                                                  UTC if the         stations.          stations.         Where: ``933'' is the 
                                                                          average snow                                             code group indicator 
                                                                          depth (to the                                            and ``RRR'' is the   
                                                                          nearest inch) is                                         water equivalent of  
                                                                          2 inches or more                                         snow on the ground   
                                                                          and staff is                                             reported in tenths of
                                                                          available.                                               inches.              
                                                                                                                                  Example: 933125.      
                                                                                                                                  Interpretation: 12.5  
                                                                                                                                   inches water         
                                                                                                                                   equivalent of snow on
                                                                                                                                   the ground.          
                                                                                                                                  Missing data          
                                                                                                                                   indicator: Not       
                                                                                                                                   reported if no solid 
                                                                                                                                   precipitation fell   
                                                                                                                                   during the past 6    
                                                                                                                                   hours or if hail was 
                                                                                                                                   the only form of     
                                                                                                                                   solid precipitation. 
Depth of snow on the ground....  ..................  X.................  At 6-hrly          Designated         Designated         Format: 4/sss.        
                                                                          synoptic times     stations.          stations.         Where: ``4/'' is the  
                                                                          (00, 06, 12, and                                         code group indicator 
                                                                          18 UTC) and                                              for depth of snow on 
                                                                          staff is                                                 the ground at        
                                                                          available. See                                           observation time.    
                                                                          comments.                                                ``sss'' gives the    
                                                                                                                                   snow depth encoded in
                                                                                                                                   whole inches with    
                                                                                                                                   leading zeros.       
                                                                                                                                  Example: 4/009.       
                                                                                                                                  Interpretation: The   
                                                                                                                                   snow depth at        
                                                                                                                                   observation time was 
                                                                                                                                   9 inches.            
                                                                                                                                  Missing data          
                                                                                                                                   indicator: Not       
                                                                                                                                   reported if the      
                                                                                                                                   frozen precipitation 
                                                                                                                                   was comprised        
                                                                                                                                   exclusively of hail. 
                                                                                                                                  Comments: Report at 00
                                                                                                                                   and 12 UTC whenever  
                                                                                                                                   there is more than a 
                                                                                                                                   trace of snow on the 
                                                                                                                                   ground and at 06 and 
                                                                                                                                   18 UTC if there is   
                                                                                                                                   more than a trace of 
                                                                                                                                   snow on wht ground   
                                                                                                                                   and more than a trace
                                                                                                                                   of precipitation     
                                                                                                                                   (water equivalent)   
                                                                                                                                   occurred within the  
                                                                                                                                   past 6 hours.        

[[Page 64027]]
                                                                                                                                                        
Synoptic total cloud cover and   ..................  X.................  At 6-hrly          Designated         .................  Format: 8NNh CL hCM   
 cloud types (low cloud base                                              synoptic times     stations.                             CH.                  
 height; low cloud amount; low,                                           (00, 06, 12, and                                        Reference: FMH-2      
 middle, and high cloud types).                                           18 UTC) unless                                           paragraph 4.2.7      
                                                                          the sky is clear.                                        modified to include  
                                                                                                                                   ``N'' (total cloud   
                                                                                                                                   cover) as described  
                                                                                                                                   in FHM-2 paragraph   
                                                                                                                                   4.2.2.1 and ``h''    
                                                                                                                                   (height of lowest    
                                                                                                                                   cloud) as described  
                                                                                                                                   in FMH-2 paragraph   
                                                                                                                                   4.2.1.3.             
                                                                                                                                  Where: ``8'' is the   
                                                                                                                                   code group indicator.
                                                                                                                                   ``N'' is total       
                                                                                                                                   fraction of oktas    
                                                                                                                                   (eighths) of the     
                                                                                                                                   celestial dome       
                                                                                                                                   covered by clouds,   
                                                                                                                                   where ``9''          
                                                                                                                                   represents sky       
                                                                                                                                   obscured by fog and/ 
                                                                                                                                   or other             
                                                                                                                                   meteorological       
                                                                                                                                   phenomena and ``/''  
                                                                                                                                   in the ``N'' position
                                                                                                                                   means cloud cover is 
                                                                                                                                   indiscernible for    
                                                                                                                                   reasons other than   
                                                                                                                                   fog or other         
                                                                                                                                   meteorological       
                                                                                                                                   phenomena, or the    
                                                                                                                                   observation was not  
                                                                                                                                   made. Nh gives the   
                                                                                                                                   total amount (oktas) 
                                                                                                                                   of all CL clouds. If 
                                                                                                                                   there are no CL      
                                                                                                                                   clouds, Nh gives the 
                                                                                                                                   total amount of all  
                                                                                                                                   CM clouds. Otherwise 
                                                                                                                                   Nh=0. Nh=9 for sky   
                                                                                                                                   obscured by fog and/ 
                                                                                                                                   or other             
                                                                                                                                   meteorological       
                                                                                                                                   phenomena. Nh=/ for  
                                                                                                                                   cloud cover          
                                                                                                                                   indiscernible for    
                                                                                                                                   reasons other than   
                                                                                                                                   fog or other         
                                                                                                                                   meteorological       
                                                                                                                                   phenomena, or if the 
                                                                                                                                   observation is not   
                                                                                                                                   made. CL, CM, and CH 
                                                                                                                                   are types of low,    
                                                                                                                                   middle, and high     
                                                                                                                                   clouds respectively. 
                                                                                                                                   ``0'' is coded for   
                                                                                                                                   clouds absent, except
                                                                                                                                   that ``/'' is coded  
                                                                                                                                   in the cloud layer   
                                                                                                                                   subfield(s) above on 
                                                                                                                                   overcast layer if the
                                                                                                                                   types are not        
                                                                                                                                   determinable. ``h''  
                                                                                                                                   gives the height with
                                                                                                                                   respect to the       
                                                                                                                                   surface of the base  
                                                                                                                                   of the lowest cloud  
                                                                                                                                   seen. It is a single 
                                                                                                                                   digit coded in       
                                                                                                                                   accordance with FMH- 
                                                                                                                                   2. Table 3-3. ``h''  
                                                                                                                                   and CL CM CH are     
                                                                                                                                   coded with ``/'' if  
                                                                                                                                   there is a total     
                                                                                                                                   surface based        
                                                                                                                                   obscuration which    
                                                                                                                                   prevents an          
                                                                                                                                   observation of the   
                                                                                                                                   clouds.              
                                                                                                                                  Example: 8220850.     
                                                                                                                                  Interpretation: N=2   
                                                                                                                                   oktas total cloud    
                                                                                                                                   cover. Scattered     
                                                                                                                                   middle clouds (Nh=2  
                                                                                                                                   oktas cloud coverage 
                                                                                                                                   and CL=0) with bases 
                                                                                                                                   between 7,000 and    
                                                                                                                                   8,000 ft AGL (h=8);  
                                                                                                                                   no low clouds; middle
                                                                                                                                   clouds are           
                                                                                                                                   altocumulus          
                                                                                                                                   progressively        
                                                                                                                                   invading the sky; no 
                                                                                                                                   high clouds.         
                                                                                                                                  Missing data          
                                                                                                                                   indicator: The ``8'' 
                                                                                                                                   group is not reported
                                                                                                                                   for clear skies.     
--------------------------------------------------------------------------------------------------------------------------------------------------------



                                                                                                                
----------------------------------------------------------------------------------------------------------------
                                               Precipitation types                                              
-----------------------------------------------------------------------------------------------------------------
               Weather                       Contraction                Weather                Contraction      
----------------------------------------------------------------------------------------------------------------
Rain.................................  R......................  Snow...................  S                      
Rain Showers.........................  RW.....................  Snow Showers...........  SW                     
Drizzle..............................  L......................  Snow Pellets...........  SP                     
Freezing Rain........................  ZR.....................  Snow Grains............  SG                     
Freezing Drizzle.....................  ZL.....................  Ice Crystals...........  IC                     
Ice Pellets..........................  IP.....................  Hail...................  A                      
Ice Pellet Showers...................  IPW....................  .......................  .......................
----------------------------------------------------------------------------------------------------------------


                                                                                                                

[[Page 64028]]
                              Table 2.--Precipitation Types and their Contractions                              
----------------------------------------------------------------------------------------------------------------
                                             Obstructions to vision                                             
-----------------------------------------------------------------------------------------------------------------
             Obstruction                     Contraction              Obstruction              Contraction      
----------------------------------------------------------------------------------------------------------------
Volcanic ash.........................  VOLCANIC ASH...........  Blowing Sand...........  BN                     
Ice Fog..............................  IF.....................  Blowing Dust...........  BD                     
Smoke................................  K......................  Blowing Spray..........  BY                     
Blowing Snow.........................  BS.....................  Fog....................  F                      
Ground Fog...........................  GF.....................  Dust...................  D                      
Haze.................................  H......................  .......................  .......................
----------------------------------------------------------------------------------------------------------------


Table 3.--Obstructions to Vision and their Contractions
Examples of Supplementary Data Reports
CAESCDCHS
TTAA00 KCHS DDHHMM
CHS SCD 1758 IP-/ 8872// 931024 933009 4/009

    This SCD shows the occurrence of weather (ice pellets) along with 
coded remarks. 8872// indicates overcast low clouds (ragged shreds of 
stratus or cumulus associated with precipitation) with low cloud base 
height of 400-600 ft. 931024 represents a 6 hour snowfall amount of 2.4 
inches. The water equivalent of snow on the ground was 0.9''. The snow 
depth (4/009) at time of observation was 9 inches.

PHLSCDPHL
TTAA00 KPHL DDHHMM
PHL SCD 0455 70050 400700045

    This SCD, issued at midnight EST, is from a WFO which does not have 
a collocated ASOS. The 24-hour precipitation total (70050) was 0.50 
inches water equivalent. The 24-hour maximum and minimum temperatures 
were 70 deg.F and 45 deg.F respectively.

BISSCDBIS
TTAA00 KBIS DDHHMM
BIS SCD 0755 98096

    This SCD from a network sunshine duration station reports 96 
minutes of sunshine for the previous calendar day.

STLSDOMCI
TTAA00 KMCI DDHHMM
MCI SDO 0642 IP-

    This SDO reports the onset of light ice pellets.

STLSDOMCI
TTAA00 KMCI DDHHMM
MCI SDO 0729 END IP

    This SDO reports the cessation of ice pellets.

PHLSDOACY
TTAA00 KACY DDHHMM
ACY SDO 0759 SNOINCR \1/2\

    This SDO indicates snow depth increase at a rate of more than 0.5 
inches/hour. The snow depth increased 1 inch during the past hour. Two 
inches of snow were on the ground at observation time.

PHLSDOACY
TTAA00 KACY DDHHMM
ACY SDO 2036 HLSTO \3/4\

    This SDO reports a hail occurrence with the largest observed 
hailstone size of \3/4\ inch.

SEASDOSMP
TTAA00 KSMP DDHHMM
SMP SDO 1756 END IP / RWU CAD LYR 140 OVC

    This SDO was reported from a mountainous site where terrain is 
problematic. Ice pellets ended. Rain showers of unknown intensity were 
observed to the southwest. There was a significant overcast cloud layer 
based at 14,000 feet above the observer's ground level. The ``/ '' 
remarks separator separates decodable and nondecodable remarks.

DENSDODEN
TTAA00 KDEN DDHHMM
DEN SDO 1056 CLD BASES OBSCG MTNS W

    This SDO was also reported from a mountainous site where terrain is 
problematic. Clouds were observed obscuring mountains to the west.

/D ANC SDO HHMM
ANC SDO 1310 IF=

    This SDO shows the initiation of ice fog. Notice that a different 
communications header and message ending code (=) are used in Alaska.

/D ANC SDO HHMM
ANC SDO 1645 END IF=

    This SDO terminates the ice fog event.

[FR Doc. 95-30246 Filed 12-12-95; 8:45 am]
BILLING CODE 3510--12-M