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NOUS41 KWBC 051929
PNSNMC
NATIONAL TECHNICAL INFORMATION MESSAGE 95-02
NATIONAL WEATHER SERVICE HEADQUARTERS
230 PM EST THU JAN 5 1995
TO: ALL USERS OF NATIONAL WEATHER SERVICE PRODUCTS
FROM: JOE FRIDAY, DIRECTOR, NATIONAL WEATHER SERVICE
SUBJECT: PROBLEMS ASSOCIATED WITH THE IMPLEMENTATION OF SURFACE
OBSERVATION CODE CHANGES ON JANUARY 1, 1995
Changes to the additive data section of the hourly surface
aviation observations taken at National Weather Service (NWS),
U.S. Air Force (USAF) and U.S. Navy sites were implemented on
January 1, 1995. However, a few USAF sites are reporting the
pressure tendency group in both the old and the new format in the
same observation. Later this month, the USAF will implement
software at Tinker Air Force Base to eliminate the double
reporting of pressure tendency groups. The Federal Aviation
Administration (FAA) will implement the additive data changes in
the next few months.
Several problems within the NWS have occurred as the result of
decoding difficulties related to the new additive format. Some
of these problems have already been corrected; additional changes
remain to be made.
The hourly surface observation decoders at the National
Meteorological Center (NMC) are not currently decoding the
additive data in the surface observations properly. These data
include the maximum and minimum temperatures, 24-hour observed
precipitation, and the pressure tendency group.
Several NMC-generated products have been affected by the decoding
difficulties, notably the Selected Cities Summaries (AFOS
identifiers NMCSCS11-14; WMO headers ABUS11-14 KWBC). HOWEVER, I
WANT TO EMPHASIZE THAT LOCAL NWS WARNING AND FORECAST PROGRAMS
ARE NOT ADVERSELY AFFECTED BY THIS PROBLEM. Similarly, the
centrally-produced statistical guidance products (such as the MOS
guidance) HAVE NOT BEEN AFFECTED.
DESCRIPTION OF IMPACT ON NMC OPERATIONAL PRODUCTS:
1. Erroneous and sparse maximum and minimum temperatures have
appeared on graphics products and in the Selected Cities
Summaries.
2. Erroneous and very sparse precipitation data affect observed
heavy precipitation graphics and forecasts and Selected
Cities Summaries.
3. Centrally-generated AFOS surface plot files may contain
erroneous pressure change data.
4. Observed snow cover affects the weekly snow cover products
which are produced by the Satellite Analysis Branch of
NESDIS, and are used in the global model.
As a first step toward correcting the problems with the Selected
Cities Summaries, NMC began using synoptic reports for maximum
and minimum temperatures and observed precipitation, beginning at
0000 UTC on January 5, 1995. As time permits, max/min
temperatures and precipitation in the Selected Cities Summaries
will be supplemented by manual intervention for cities for which
synoptic observations are not available. All other stations'
max/min temperatures will be designated as missing with "M" until
further solutions are implemented (see below).
Until all the problems with the Selected Cities Summaries are
resolved, the following message will be appended to the end of
the Selected Cities bulletin: "Due to data processing problems,
the 'selected cities' station observation listing is not
complete. Efforts continue to correct the problem as quickly as
possible. Local NWS warning and forecast programs have NOT been
effected by this problem."
PLAN FOR FIXING THE PROBLEMS IN THE SELECTED CITIES BULLETINS:
* By 0000 UTC on January 6, 1995, NMC plans to supplement the
January 5th fix (described above) using max/min temperature
data from all hourly surface observing stations included in the
bulletin. Precipitation from the hourlies for cities in the
bulletin will be missing (designated by "M").
* By 0000 UTC on January 7, 1995, the precipitation data will be
added to the bulletins, based on hourly surface observations.
PLAN FOR FIXING PROBLEMS OTHER THAN IN THE SELECTED CITIES
SUMMARIES:
* Pressure tendency, snow cover, cloud type, and other possible
changes, including graphics products, are being addressed as
quickly as possible.
Additional status reports will be issued as progress is made.
Users may also refer to the Senior Duty Meteorologist's status
message (AFOS identifier NMCADMNFD; WMO header NOUS42 KWBC) for
status information.
If you have any questions, call Jim Howcroft, Deputy Director of
NMC, at (301)-763-8181 or Ralph Petersen, Acting Chief of NMC's
Meteorological Operations Division, at (301)-763-8097.
END
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