All,

You are receiving this message because you have been identified as a
user of NCEP model data.

Users reported some problems with the GFS model changes which were implemented on Sep 25 2007.  NCEP's EMC and NCO have coordinated and tested a package which addresses these problems.  The results have been verified by parties in the public and private sectors.

This improved GFS package will be implemented on Oct 10 2007 at 12Z.

The specific problems addressed are:

Grid Interpolation: A change will be made to the interpolation routine for AWIPS and WAFS products, as well as GFS grids sets sent to public servers. The change will reflect a more consistent bi-linear interpolation.  This will remove much of the noise observed in contours, as well as soil/land inconsistencies.

Spurious High Pressure over Mountainous Coasts: A change to the GFS post codes will remove a persistent, spurious high pressure system observed over Hawaii and the Alaskan coast.

If you encounter any problems with this GFS implementation, please contact the following PMB Data Flow helpdesk email address with your concern.

NCEP.PMB.Dataflow@noaa.gov

Thank you and we apologize for any inconvenience this model change may have caused.

NCEP/NCO/PMB

End of Message.


All,

You are receiving this message because you have been identified as a
user of NCEP model data on the NCEP and/or NWS ftp servers.

The GFS model will be upgraded on Sep 25 2007.  The most significant
impact of this change will result in grib1 and grib2 files which are
10-30% larger than with the current GFS.  A few other changes are
occurring in the modeling system.  Please see the NWS TIN which is attached.

All other changes to NCEP modeling systems can be found at the following
website:
http://www.nco.ncep.noaa.gov/pmb/changes/

Thanks,
Joey Carr

SUBJECT:  UPGRADE TO NCEP GLOBAL FORECAST SYSTEM /GFS/

EFFECTIVE TUESDAY SEPTEMBER 25 2007...WITH THE 1200 COORDINATED
UNIVERSAL TIME /UTC/ RUN...THE NATIONAL CENTERS FOR ENVIRONMENTAL
PREDICTION /NCEP/ WILL UPGRADE THE GFS POST PROCESSOR.

THE PRIMARY EFFORT BEHIND THIS UPGRADE WILL BE TO UNIFY THE POST
PROCESSING CODE FOR THE NORTH AMERICAN MESO SCALE /NAM/ MODEL AND THE
GFS INTO THE NEW NCEP POST. AFTER THE UPGRADE...BOTH THE NAM AND GFS
MODELS WILL BE ABLE TO GENERATE FIELDS ORIGINALLY CREATED FOR EACH
UNIQUE MODEL.

THE PRIMARY IMPACT TO CUSTOMERS RECEIVING THE GFS WILL BE THAT THE
DEFAULT PRECIPITATION TYPE ALGORITHM WILL CHANGE FROM THE BALDWIN METHOD
TO THE DOMINANT PRECIPITATION TYPE.  THE DOMINANT PRECIPITATION TYPE IS
DETERMINED BY TAKING THE PREDICTED TEMPERATURE AND MOISTURE PROFILES AND
RUNNING THEM THROUGH FIVE ALGORITHMS: BALDWIN (NCEP)...REVISED
NCEP...RAMER...BOURGOUIN
...AND AN EXPLICIT MICROPHYSICS ALGORITHM.  AT EACH POINT...THE CODE
DETERMINES WHICH PRECIPITATION TYPE WAS PREDICTED BY THE MAJORITY OF THE
ALGORITHMS AND USES THAT AS THE DOMINANT TYPE.  TIES ARE BROKEN IN FAVOR
OF THE MORE DANGEROUS WEATHER (ZR>SN>IP>RA).

IN ADDITION...THE SAME ALGORITHMS WILL BE USED TO DERIVE MOST FIELDS FOR
THE TWO MODELS.

THE PRODUCTS/GRIDS WHICH ARE DISSEMINATED TO NOAAPORT AND/OR THE
SATELLITE BROADCAST NETWORK /SBN/ WILL NOT BE CHANGED IN VOLUME OR CONTENT.

NCEP CENTRAL OPERATIONS IS CURRENTLY RUNNING A REAL-TIME PARALLEL.
RESULTS FROM THESE PARALLEL RUNS CAN BE VIEWED AT /USE LOWER CASE LETTERS/:

HTTP://WWW.NCO.NCEP.NOAA.GOV/PMB/NWPARA/ANALYSIS/

IF YOU HAVE ANY QUESTIONS CONCERNING THESE CHANGES...PLEASE CONTACT:

DR MARK IREDELL
NCEP/EMC...CHIEF GLOBAL MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301 763 8000 X7231
EMAIL: MARK.IREDELL@NOAA.GOV

OR

KEN CAMPANA
NCEP/EMC...GLOBAL MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301 763 8000 X7228
EMAIL: KENNETH.CAMPANA@NOAA.GOV