NOUS41 KWBC 061105 AAA



Service Change Notice 17-45 Updated

National Weather Service Headquarters Silver Spring, MD

705 AM EDT Tue Jun 6 2017.


To:       Subscribers:

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Dave Myrick

          NWS Office of Science and Technology Integration


Subject:  Updated: Discontinue GFDL Hurricane Model:

          Effective July 5, 2017


Updated the effective change date


The National Centers for Environmental Prediction (NCEP) will

retire the Geophysical Fluid Dynamics Laboratory (GFDL)

Hurricane Model (GHM) on July 5, 2017. With the GFS upgrade it

will be replaced with a new NOAA Environmental Modeling System

(NEMS)-based hurricane model called HMON (Hurricanes in a Multi-

scale Ocean-coupled Non-hydrostatic) in NCEP operations.


A public comment period was open between Feb 13, 2017, to March

17, 2017, soliciting feedback for discontinuing the GFDL and

replacing it with the HMON system. Based on comments NCEP will

move forward executing this plan. Please see the PNS if you have

any questions:


NCEP is retiring the legacy GFDL Hurricane Model for the

following reasons:


1. The Environmental Modeling Center's (EMC) efforts towards

unification of operational models within the NEMS framework.


2. NHC's evaluation and endorsement of the new hurricane model

(HMON) through evaluation of 3-year (2014-2016) retrospective

experiments run by EMC. HMON model consistently showed improved

performance for track and intensity skill for the North Atlantic

and Northeast Pacific Basins as compared to the legacy GFDL

hurricane model.


3. Retirement of key personnel at GFDL leading to a loss of

support for maintaining the GFDL Hurricane model in operations.


The timing of the proposed changes will be as follows:


1. The GHM will be discontinued on the date of the GFS2017

upgrade sometime in June 2017. This SCN will be updated with the

exact date once it is known. On that date, all GHM products will

be removed from the following:


 - NCEP servers under hur.YYYYMMDD will be discontinued:

   Where YYYYMMDD is year, month and day


 - Model Analyses and Guidance will be discontinued:


2. With the hurricane model upgrade slated for June 2017, NCEP

will start delivering the new operational model, HMON, on the

NCEP servers. The replacement product output of the HMON will be

equivalent to the discontinued GHM, for sample data please



Send questions, comments or requests to:


     Avichal Mehra

     Lead, Physical Scientist

     NCEP/Environmental Modeling Center

     College Park, MD


     Carissa Klemmer

     NWS/NCEP Central Operations

     Dataflow Team Lead

     College Park, MD


National Service Change Notices are online at: