NOUS41 KWBC 221542



Technical Implementation Notice 12-51

National Weather Service Headquarters Washington DC

1142 AM EDT Mon Oct 22 2012


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Timothy McClung

           Chief, Science Plans Branch

           Office of Science and Technology


Subject:   Change to Parameters and Precision in RAP Native           Files: Effective November 27, 2012


Effective on or about Tuesday, November 27, 2012, beginning with the 1200 Coordinated Universal Time (UTC) run, the National Centers for Environmental Prediction (NCEP) will make changes to the 13 and 20 km native bgrb files from the Rapid Refresh (RAP) model.  The content will change for the files for forecast hours 04, 07, 10, 13, and 16, while the precision of the pressure on native levels records will change for all files.  There changes affect only the bgrb output; there are no changes to any of the other RAP output files. These files are available in the following locations:


NWS FTP server:


where hh is the model cycle from 00 to 23


NCEP server:


The RAP bgrb files contain data on native model levels along with a few additional parameters. These files should contain 1-hr stratiform and convective precipitation data at forecast hours 1, 4, 7, 10, 13, and 16.  They do contain 2-hr stratiform and convective precipitation data at forecast hours 2, 5, 8, 11, 14, and 17, and they do contain 3-hr stratiform and convective precipitation data at forecast hours 3, 6, 9, 12, 15, and 18. The 1-hr precipitation data is currently missing for forecast hours 4, 7, 10, 13, and 16 and will be added to those files with this change.


These files contain data for pressure values on native model levels, and the precision will be changed for all 50 records. The current decimal scale factor is -2, while the binary scale factor is 1.   These values will both become 0 with the changes to give more precision to these records.


The changes result in the size of the 13 km grib2 files increasing from approximately 30.5 MB each to approximately 34.5 MB. The size of the 20 km grib2 files increases from approximately 16.0 to 18.2 MB.  NCEP urges all users to ensure their decoders can handle these changes. Sample forecast hour f04 modified native files at both
13 and 20 km resolution can be found at:


For questions regarding these changes, please contact:


    Geoff Manikin

    NCEP/EMC/Mesoscale Modeling Branch

    College Park, MD



For questions regarding the dataflow aspects of these datasets, please contact:


    Rebecca Cosgrove

    NCEP/NCO Dataflow Team

    College Park, MD



NWS National Technical Implementation Notices are online at: