NOUS41 KWBC 091500
Technical Implementation Notice 16-17
National Weather Service Headquarters Washington DC
1100 AM EDT Thu Jun 9 2016
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
Other NWS Partners, Users and Employees
From: Timothy McClung
NWS Office of Science and Technology Integration
Subject: GFDL Hurricane Prediction System Changes:
Effective July 12, 2016
Effective on or about Tuesday, July 12, 201,6 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:
- Modified detrainment of micro-physics in the Simplified
Arakawa-Schubert (SAS) convection scheme
- Modified convective time scale in calling of SAS convection.
- Bug Fixes in the SAS scheme
- Improved representation of the storm initial wind profile
- Changed Ocean Initialization to run with Real Time Ocean
Forecast System (RTOFS) analysis in the Eastern Pacific
- Added new functionality to ingest Global Forecast System (GFS)
GRIB data to create the lateral boundary condition.
Extensive testing over multiple hurricane seasons show
significant improvements in the prediction of storm track and
intensity in both the Atlantic and Eastern Pacific basins.
Reductions in track error averaged 25 percent in the 4-5 day
lead times in the Atlantic and about 17 percent in the Eastern
Pacific at days 3-5.
Intensity errors decreased about 15 percent in the 3-5 days lead
times in the Atlantic. With better representation of the
hurricane-ocean interaction in the Eastern Pacific through the
introduction of the RTOFS analysis, the cooling in the cold
wakes will be significantly reduced, increasing the reliability
of the model to predict rapid intensity change events.
Impact to Output Products:
The GFDL hurricane model GRIB products are disseminated via the
NCEP and NWS FTP servers and are not available on NOAAPORT or
In NWS TIN 15-26
NWS announced that the GRIB1 output from the GFDL would be
discontinued in the 2016 hurricane season given that it had been
replaced by GRIB2. Therefore, all GRIB1 output files will be
removed from our servers with this upgrade. This means all the
(where xx = cycle) will be removed.
On the NCEP ftp server
and at NOMADS:
in directories hur.YYYYMMDDCC (where YYYYMMDDCC is the year,
month, day and cycle) only the files with *grib2 on the end and
*.stats.short will remain.
There are no changes to existing GRIB2 output content, however
forecast products will be available about 10 minutes earlier due
to the use of GRIB 2 data for the lateral boundary generation.
More details about the GFDL hurricane prediction system are
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. 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:
For questions regarding the data flow aspects of these data
sets, please contact:
NCEP/NCO Dataflow Team Lead
College Park, MD
NWS National Technical Implementation Notices are online at: