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PNSWSH

TECHNICAL IMPLEMENTATION NOTICE 10-15... AMENDED NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC 158 AM EDT MON JUL 19 2010

TO:

FROM:

SUBJECT:

REFER TO:

DUE TO THE COMPLEXITY OF THE IMPLEMENTATION OF THE GLOBAL FORECAST SYSTEM AND ALL DOWNSTREAM DEPENDENCIES...THE EFFECTIVE DATE OF THE UPGRADE IS BEING RESCHEDULED FOR WEDNESDAY JULY 28. IF THE NWS DECLARES A CRITICAL WEATHER DAY ON OR AROUND JULY 28 THE IMPLEMENTATION MIGHT BE DELAYED. ANOTHER TIN WILL BE SENT IF THIS OCCURS.

EFFECTIVE JULY 28 2010...BEGINNING WITH THE 1200 COORDINATED UNIVERSAL TIME /UTC/ RUN...THE NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION /NCEP/ WILL UPGRADE THE GLOBAL FORECAST SYSTEM /GFS/. THE RESOLUTION OF THE GLOBAL FORECAST MODEL WILL BE INCREASED FROM T382 /35 KM/ TO T574 /27 KM/. THE HIGH RESOLUTION PORTION OF THE FORECAST WILL BE EXTENDED FROM 180 HRS TO 192 HRS. WITH THIS EXTENSION 3 HOURLY OUTPUT WILL BE MADE AVAILABLE OUT TO 192 HOURS.

THIS WILL RESULT IN SIGNIFICANT CHANGES IN THE DEFINITION OF PARAMETERS IN THE 192 HOUR PRESSURE GRIB /PGRB/ AND FLUX FILES. THERE WILL ALSO BE SIGNIFICANT CHANGES IN MODEL PHYSICS ASSOCIATED WITH THIS CHANGE. IN ADDITION MODIFICATIONS WILL BE MADE TO THE CONTENTS OF THE GLOBAL DATA ASSIMILATION SYSTEM /GDAS/ AND GFS PGRB FILES.

CHANGES IN MODEL PHYSICS INCLUDE:

THE NEW PARAMETER FOR THE GFS FORECAST PRESSURE GRIB FILE IS:

SEVERAL PARAMETERS ARE BEING DELETED FROM THE GDAS ANALYSIS PRESSURE GRIB FILES BECAUSE THEY ARE NOT VALID FOR THE ANALYSIS DATASET AND HAVE NEVER PROVIDED PERTINENT INFORMATION. THESE INCLUDE:

THESE PARAMETERS ARE BEING DELETED FROM THE GLOBAL FORECAST MODEL SIMULATED GOES GRIB FILE BECAUSE THEY WERE INCLUDED IN ERROR. THESE FIELDS ARE AVAILABLE IN THE PGRB FILES:

ALL ACCUMULATED OR AVERAGED VALUES IN THE 192 HOUR PGRB AND FLUX FILES WILL NOW BE OVER A 6 HOUR PERIOD INSTEAD OF 12 HOURS. THE FORMAT AND CONTENT OF THE 3 HOURLY FILES FROM 180 TO 192 HOURS WILL BE THE SAME AS THE FILES FROM 0 TO 180. FOR THE FLUX FILE...THIS INCLUDES THE MAJORITY OF THE PARAMETERS IN THE FILE. PARAMETERS CHANGING IN THE PGRB FILE ARE:

NOTE THAT FOR THE 192 HR PGRB PRODUCTS AVAILABLE ON NOAAPORT AND IN AWIPS... THE ACCUMULATIONS AND AVERAGES WILL REMAIN OVER THE PREVIOUS 12 HOUR PERIOD UNTIL AWIPS IS MODIFIED TO ACCOMMODATE THIS CHANGE.

ONE ADDITIONAL CHANGE TO NOTE IS THAT THE FILE PGRBF192.GRIB2 ON THE NCEP FTP SERVER WILL CHANGE FROM CONTAINING MODEL OUTPUT ON A 2.5 DEGREE GRID TO CONTAINING MODEL OUTPUT ON A 1 DEGREE GRID. THE 2.5 DEGREE OUTPUT WILL BE PROVIDED IN A NEW FILE WITH THE NAME PGRBF192.2P5DEG.GRIB2.

THE FORMAT OF THE HALF AND ONE DEGREE PRESSURE GRIB FILES WILL REMAIN THE SAME EXCEPT FOR THE CHANGES IN VARIABLES LISTED ABOVE. THE SIZE OF THESE FILES WILL NOT CHANGE SIGNIFICANTLY. WITH THE INCREASE IN MODEL RESOLUTION...THE SIZE OF THE SIGMA COEFFICIENT FILES AND THE SURFACE FLUX FILES WILL INCREASE SIGNIFICANTLY.

THESE CONTENT CHANGES WILL IMPACT ALL DISSEMINATION ROUTES: NWS PUBLIC FTP SERVER...THE NCEP PUBLIC FTP SERVER AND NOAAPORT.

A SET OF TEST DATA IS AVAILABLE /USE LOWERCASE/::
FTP://FTP.EMC.NCEP.NOAA.GOV/GC_WMB/WX24FY/GFS_T574L64/GFS.20091217/

A CONSISTENT PARALLEL FEED OF DATA IS AVAILABLE ON THE NCEP FTP SERVER AT THE FOLLOWING URL /USE LOWERCASE/:

FTP://FTP.NCEP.NOAA.GOV/PUB/DATA/NCCF/COM/GFS/PARA

DATA DELIVERY TIMING OF THE GFS WILL NOT BE IMPACTED BY THIS IMPLEMENTATION.

NCEP ENCOURAGES ALL USERS TO ENSURE THEIR DECODERS ARE FLEXIBLE AND ARE ABLE OF ADEQUATELY HANDLING CHANGES IN CONTENT... PARAMETER FIELDS CHANGING ORDER...CHANGES IN THE SCALING FACTOR COMPONENT WITHIN THE PRODUCT DEFINITION SECTION /PDS/ OF THE GRIB FILES AND ANY VOLUME CHANGES WHICH MAY OCCUR. THESE ELEMENTS MAY CHANGE WITH FUTURE NCEP MODEL IMPLEMENTATIONS. NCEP WILL MAKE EVERY ATTEMPT TO ALERT USERS TO THESE CHANGES PRIOR TO ANY IMPLEMENTATIONS.

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

JOHN H. WARD
NCEP...GLOBAL MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301-763-8000 X7185
EMAIL: [email protected]
OR
SHRINIVAS MOORTHI
NCEP...GLOBAL MODELING BRANCH
CAMP SPRINGS MARYLAND
PHONE: 301-763-8000 X7233
EMAIL: [email protected]

NWS NATIONAL TECHNICAL IMPLEMENTATION NOTICES ARE ONLINE AT:

HTTP://WWW.WEATHER.GOV/OS/NOTIF.HTM
$$ NNNN

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