NOUS41 KWBC 011227



Technical Implementation Notice 15-22

National Weather Service Headquarters Washington DC

825 AM EDT Fri May 1 2015


To:        Subscribers:

           -Family of Services

           -NOAA Weather Wire Service

           -Emergency Managers Weather Information Network


           Other NWS Partners, Users and Employees


From:      Timothy McClung

           Chief Operating Officer          

           NWS Office of Science and Technology Integration


Subject:  Changes to NAM DNG and DGEX, including addition of

          Haines Index to NOAAPORT Effective June 2, 2015


Effective on or about Tuesday, June 2, 2015, beginning with the

1200 Coordinated Universal Time (UTC) run, the National Centers

for Environmental Prediction (NCEP) will make the following

modifications to the Downscaled Numerical Guidance (DNG) from the

NAM analysis and forecast system and from the downscaled GFS by

NAM extension (DGEX) forecast system:


- Correct the wind adjustment algorithm in regions where the

terrain height is below sea level: This change will correct

erroneously large adjusted wind speeds seen in NAM DNG in the

vicinity of the Salton Sea in California.

- Change the AWIPS Haines Index calculation to use the correct

dew-point depression and intercept and to ensure that it is a

whole number between 2 and 6 over land, as defined in the

original formulation of the index by Haines (1988, National

Weather Digest)

- Fix labeling problem. The NAM DNG and DGEX DNG GRIB2 files at

forecast hours not divisible by 12 also contain hourly

temperatures, for example, the hour 3 file contains hour 1 and 2

temperatures. This process is done for the calculation of the 12-

h maximum and minimum temperatures; however, the forecast hour

was mislabeled for these hourly temperatures, i.e., in the 3-hour

file, hour 2 was mislabeled as hour 1, and hour 1 was mislabeled

as hour 2. This has been fixed in this package.


In addition, the Haines Index parameters from the NAM DNG and

DGEX will be disseminated via NOAAPORT on this date.  The WMO

headers for the products are as follows:


NAM DNG CONUS 2.5 km (hours 00 - 60): tZIa98 KWBE

NAM DNG CONUS  5 km  (hours 63 - 84): tZOa98 KWBE

NAM DNG Alaska 3 km  (hours 00 - 60): tZKa98 KWBE

NAM DNG Alaska 6 km  (hours 63 - 84): tZAa98 KWBE


t = L for forecast hours 00,06,12,18,24,30,36,42,48,60,72,84

t = M for forecast hours 03,09,15,21,27,33,39,45,51,54,57,63,





a = forecast hour, where A=00, B=03 or 06, C=12, D=18, E=09 or

    24, F=30, G=36, H=15 or 42, I=48, J=60, K=21 or 72, L=27 or

    84, M=54, N=66, O=33, P=39, Q=45, R=51, S=57, T=78, Z= 63,

    69, 75, 81


DGEX CONUS (hours 87 to 192, every 3 hours):  tZOa98 KWBD

DGEX Alaska(hours 87 to 192, every 3 hours):  tZAa98 KWBD,


t = Y for forecast hours 96, 108, 120, 132, 144, 156, 168, 180,


t = Z for forecast hours 87, 90, 93, 99, 102, 105, 111, 114, 117,

    123, 126, 129, 135, 138, 141, 147, 150, 153, 159, 162, 165,

    171, 174, 177, 183, 186, 189




a = forecast hour, where M=96, N=108, O=120, P=132, Q=144, R=156,

    S=168, T=180, U=192, and all other hours between 87 and

    192 = Z


The NAM DNG and DGEX, including the Haines Index parameter, are

available today via the following URLs:


A set of output files with the fixes above are provided at:






Please ensure your decoders can handle changes in content order,

changes in the scaling factor component within the product

definition section (PDS) of the GRIB files, and volume changes.

These elements may change with future NCEP model implementations.

NCEP will make every attempt to alert users to these changes

before implementation.


For questions regarding these changes, please contact:


      Geoff DiMego

      NCEP/Mesoscale Modeling Branch

      College Park, MD



For questions regarding the dataflow aspects of these datasets,

please contact:


     Kelly Kempisty

     NCEP/NCO Dataflow Team

     College Park, MD



NWS National Technical Implementation Notices are online at: