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PNSWSH

Technical Implementation Notice 12-38

National Weather Service Headquarters Washington DC

810 AM EDT Thu Aug 23 2012

To: Subscribers:

-Family of Services

-NOAA Weather Wire Service

-Emergency Managers Weather Information Network

-NOAAPORT

Other NWS Partners, Users and Employees

From: Timothy McClung

Chief, Science Plans Brach

Office of Science and Technology

Subject: GRIB2 encoding change to NCEP products:

Effective September 18, 2012

On Tuesday, September 18, 2012, National Centers for

Environmental Prediction (NCEP) will make a change to the GRIB2 encoding of the Haines Index (HINDEX) and Relative Humidity with respect to Precipitable Water (RHPW) fields. For the Haines Index (HINDEX), the GRIB2 parameter number will change from 3 to 2 to conform with WMO standards. The Relative Humidity with respect to Precipitable Water currently is encoded as discipline 0, category 19. It will change to be encoded as discipline 0, category 1.

More details about NCEP’s method of GRIB2 encoding are online at:

http://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc.shtml

These two products are currently available in output files from many NCEP models including the GFS, NAM, SREF and RAP. The output from these models is available on the NWS and NCEP ftp servers. These fields are not sent to NOAAPORT or AWIPS, so this change should not affect those users.

For questions regarding these changes, please contact:

Rebecca Cosgrove

NCEP Central Operations

College Park, Maryland

Phone: 301-683-0567

rebecca.cosgrove@noaa.gov

NWS National Technical Implementation Notices are online at:

http://www.nws.noaa.gov/os/notif.htm

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