NOUS41 KWBC 301104
Technical Implementation Notice 12-18
National Weather Service
Headquarters Washington DC
704 AM EDT Fri Mar 30 2012
To: Subscribers:
-Family of Services
-NOAA Weather Wire Service
-Emergency Managers Weather Information Network
-NOAAPORT
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 15, 2012
Effective on or about Tuesday, May 15, 2012, 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:
- Bug fix in PBL scheme
from 2003 implementation
- Bug fix in Simplified
Arakawa-Schubert (SAS) deep convection
from 2010
implementation
- Implementation of GFS Shallow Convection
- Modification of the
surface exchange coefficient (ch, cd)
- Modifications to GFS PBL scheme and momentum mixing term in
SAS deep convection
-
Detrained micro-physics generated in SAS and passed to
Ferrier micro-physics scheme
- Reduced specification of
storm size for larger storms
In tests of storms from the 2011 Atlantic hurricane season, these improvements resulted in an average reduction of track forecast error of about 12 percent in the 2 to 5 day forecast time periods. The average reduction in intensity errors averaged nearly 20 percent in the Atlantic basin during the same forecast time periods for the 2011 Atlantic hurricane season, primarily through elimination of the large positive intensity bias.
Product Changes:
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 content or dissemination time.
The GFDL data is available
on the NWS ftp server at:
ftp://tgftp.nws.noaa.gov/SL.us008001/ST.opnl/MT.ghm_CY.xx where xx is the model cycle,
and at the NCEP servers at:
www.ftp.ncep.noaa.gov/data/nccf/com/hur/prod/hur.YYYYMMDDHH
and
ftp.ncep.noaa.gov/pub/data/nccf/com/hur/prod/hur.YYYYMMDDHH
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:
http://www.gfdl.noaa.gov/operational-hurricane-forecasting
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
gfdl/noaa
Princeton, nj
Phone: 609-452-6559
Timothy Marchok
gfdl/noaa
Princeton, NJ
Phone: 609-452-6534
NWS National Technical
Implementation Notices are online at:
http://www.nws.noaa.gov/os/notif.htm
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