>I have had a couple of users complain about changes in the GFS data
>starting with the 1200 UTC run on 25 September. I notice there is a
>jump up in the size of the gempak files starting with that run. Does
>anyone know of any changes? If you are curious about what I am talking
>about, look at this page, which uses the 0.5 degree data:
>
>http://www.atmos.washington.edu/~hakim/loop.psp?url=~hakim/tropo/theta/
>
>Start the loop and look at the areas in white go from smooth to noisy
>with the 1200 UTC 25th run. Another user is now having problems with
>his WRF initialization that he did not have before this.
I just received the following:
>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@xxxxxxxx
>
>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@xxxxxxxx
>
>OR
>
>KEN CAMPANA
>NCEP/EMC...GLOBAL MODELING BRANCH
>CAMP SPRINGS MARYLAND
>PHONE: 301 763 8000 X7228
>EMAIL: KENNETH.CAMPANA@xxxxxxxx
Kevin W. Thomas
Center for Analysis and Prediction of Storms
University of Oklahoma
Norman, Oklahoma
Email: kwthomas@xxxxxx
