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NOUS41 KWBC 101830
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Service Change Notice 25-51
National Weather Service Headquarters Silver Spring MD
230 PM EDT Thu Jul 10 2025

To:  Subscribers:
     -NOAA Weather Wire Service
     -Emergency Managers Weather Information Network
     -NOAAPort
  Other NWS Partners, Users and Employees

From:  Dave Michaud
     Director
     NCEP Central Operations

Subject: Update for ObsProc Observation processing for GFS, GDAS
and NAM, Effective August 11, 2025

Effective on or about August 11, 2025, beginning with the 1200
Coordinated Universal Time (UTC) model distribution, the
National Weather Service will update Observation Processing
(ObsProc). In the event the implementation date is declared a
Critical Weather Day (CWD), an Enhanced Caution Event (ECE), or
other significant weather is occurring or is anticipated to
occur, implementation of this change will take place at 1200 UTC
on the next weekday not declared a CWD and when no significant
weather is occurring.

Changes to data products with this upgrade include:

(1) An upgrade to the Observation Processing (ObsProc) software
package to include synoptic surface observations of snow in new
global (GFS and GDAS) *sfcsno* Binary Universal Form for the
Representation of meteorological data (BUFR) dump files.

The NCEP Automated Data Processing surface weather observations
are currently stored in the *adpsfc* BUFR dumps (prioritizing
the BUFR formatted messages over the TAC when both are
available), and now in the *sfcsno* dumps reports where snow
information would be given precedence over reports without snow
information (regardless of TAC or BUFR formatting).

(2) Remove the Indian National Satellite System (INSAT) derived
satellite winds (aka AMV)from global (GFS and GDAS) *satwnd*
BUFR dump files. This change does not impact GFS and GDAS data
assimilation systems as the INSAT AMVs were not assimilated.

(3) Remove the CONUS satellite winds (aka AMV)from global (GFS
and GDAS) *satwhr* (BUFR) dump files. This change does not
impact GFS and GDAS as these AMVs were not assimilated.

(4) Correct the timing of the creation of the following
unrestricted NAM prepbufr files:
      nam.t00z.prepbufr.tm02.nr
      nam.t00z.prepbufr.tm03.nr
      nam.t00z.prepbufr.tm04.nr
      nam.t00z.prepbufr.tm05.nr
      nam.t00z.prepbufr.tm06.nr
These files were previously created 24 hours late. They will now
be created on time.

These updates will be available under the corresponding model
subdirectory:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/obsproc/prod/
ftp://ftpprd.ncep.noaa.gov/data/nccf/com/obsproc/prod/

(1) Added new dump files:
   GFS and GDAS *sfcsno.tm00.bufr_d.nr

(2) Updated contents in dump files:
   GFS and GDAS *satwnd.tm00.bufr_d

(3) Updated contents in dump files:
   GFS and GDAS *satwhr.tm00.bufr_d

All of the above updated BUFR dump files will be generated at
the temporal frequency of the existing observational products.

NCEP encourages users to ensure their processing is flexible to
adequately handle the new data. Even though content within the
*satwnd* and *satwhr* files have changed, downstream file
readers should not need to change in response.

For any comments/feedback on the BUFR dump file upgrade at the
Environmental Modeling Center (EMC), please contact:

Dr. Daryl Kleist
Chief, Data Assimilation and Quality Control Group
NCEP Environmental Modeling Center
College Park, MD
Email: daryl.kleist@noaa.gov or obsproc_support@noaa.gov


For questions regarding the dataflow aspects, please contact:

Margaret Curtis
NCEP Central Operations Dataflow Team
ncep.pmb.dataflow@noaa.gov

National Service Change Notices are online at:

https://www.weather.gov/notification