NOUS41 KWBC 221253  


Technical Implementation Notice 11-09

National Weather Service Headquarters Washington DC

853 AM EDT Tue Mar 22 2011


To:       Subscribers:

          -Family of Services

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Timothy McClung

          Science Plans Branch Chief

          Office of Science and Technology


Subject:  Hurricane Weather and Research Forecast (HWRF) Model

          Changes: Effective May 17, 2011


Effective Tuesday, May 17, 2011, beginning with the 1200

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

Environmental Prediction (NCEP) will upgrade the HWRF - Princeton

Ocean Model (POM) coupled system. The scientific enhancements

include the following:


- Upgrade WRF NMM dynamic core from v2.0 to v3.2

- Modify vortex size corrections based on radius of  

  outermost closed isobar (ROCI) and radius of 34kt winds

- Upgrade HWRF Grid point Statistical Interpolation (gsi)

  analysis scheme to community version 2.5

- Upgrade Simplified Arakawa-Schubert (SAS) deep convection

  parameterization to new version implemented in the NCEP

  Global Forecast System (GFS)

- Modify surface enthalpy exchange coefficient at high

  wind speeds

- Expand coupled region in the Eastern Atlantic domain to

  prevent storms from loosing coupling effect with the ocean

  due to insufficient overlap with the Western Atlantic region

- Upgrade HWRF post-processing to new NCEP Unified Post

  Processor (UPP)


Test results from the combination of these upgrades showed

improved track and intensity forecast skill, reduced initial

growth of errors (spin-up and spin-down) and reduced intensity

bias for the Atlantic and a majority of the eastern North

Pacific basins.


Product Changes:


The following elements will be added to the HWRF model output

GRIB files:

- Angle corrected simulated goes satellite imagery products

  /infrared and water vapor channels/

- Simulated microwave satellite imagery products

- Additional vertical pressure levels for three-dimensional



The frequency of model output will be increased from 6 hourly to

3 hourly for all variables


The HWRF GRIB products are disseminated via the NCEP and NWS FTP

servers and are not available on NOAAPORT or AWIPS.  These changes

will result in no change in product dissemination time.  There will

be an increase of roughly 2GB in product size due to the

additional elements. 


More details about the HWRF-POM are available at:


NCEP encourages users to ensure their decoders are flexible and 
are able to adequately handle changes in content order, changes 
in the scaling factor component within the product definition 
section (PDS) of the GRIB files, and any volume changes which 
may be forthcoming. These elements may change with future NCEP 
model implementations. NCEP will make every attempt to alert 
users to these changes prior to any implementations.


For questions regarding these model changes...please contact:


  Dr. Vijay Tallapragada

  NCEP/Environmental Modeling Center

  Hurricane Forecast Project

  Camp Springs, Maryland

  301-763-8000 x 7232


NWS National Technical Implementation Notices are online at: