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NOTICE: This version of the NSF Unidata web site (archive.unidata.ucar.edu) is no longer being updated.
Current content can be found at unidata.ucar.edu.
To learn about what's going on, see About the Archive Site.
>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
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