NOUS41 KWBC 151418


Technical Implementation Notice 11-11

National Weather Service Headquarters Washington DC

1018 AM EDT Fri Mar 25 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:  GFDL Hurricane Prediction System 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

Geophysical Fluid Dynamics Laboratory (GFDL) Hurricane

Prediction System. The scientific changes to the model

include the following:


- Upgrade Simplified Arakawa-Schubert (SAS) deep convection

  parameterization to new version implemented in the NCEP

  Global Forecast System (GFS)

- Modify the surface enthalpy exchange coefficient and

  dissipative heating effect

- Expand coupled region in the Eastern Atlantic domain
  to prevent storms from losing coupling effect with the
  ocean due to insufficient overlap with the Western Atlantic

  region.  The new overlap will be 25 degrees.

- Correct several bugs in the model.


In testing, these improvements resulted in an average reduction

of forecast error of about 20 percent in the Atlantic basin

for the 3 to 5 day forecast period for tests of storms from

the 2010 Atlantic hurricane season.


Product Changes:


The following will be added to the GFDL model output GRIB files:


Model-predicted 10 meter winds will be outputted in addition

to the lowest model level 35 meter winds.


The GFDL hurricane model 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 only a minor increase in product size. 

Once implemented, the GFDL data will be available on the NWS

ftp server at:

where xx is the model cycle

and at the NCEP servers at:

where YYYY is year, MM is month, DD is day, and HH is model cycle.


More details about the GFDL hurricane prediction system are available at:


NCEP encourages all 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 also 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:


Morris Bender


Princeton , nj

Phone: 609-452-6559


Timothy Marchok


Princeton , NJ

Phone: 609-452-6534



NWS National Technical Implementation Notices are online at: