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676
NOUS41 KWBC 221919
PNSNMC
NATIONAL TECHNICAL IMPLEMENTATION MESSAGE 98-19
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
330 PM EDT TUE SEP 22 1998
TO: FAMILY OF SERVICES /FOS/ SUBSCRIBERS...NOAA WEATHER
WIRE SERVICE /NWWS/ SUBSCRIBERS...OTHER NATIONAL
WEATHER SERVICE /NWS/ CUSTOMERS...NWS EMPLOYEES
FROM: LEROY SPAYD...CHIEF...SCIENCE AND TRAINING CORE
SUBJECT: CHANGES TO THE NCEP GLOBAL ANALYSIS/FORECAST
SYSTEM...EFFECTIVE SEP 28 1998
BEGINNING WITH THE 12Z GLOBAL MODEL RUN ON SEP 28 1998 /BARRING
UNFORSEEN PROBLEMS OR A CRITICAL WEATHER DAY/...SEVERAL CHANGES
WILL BE IMPLEMENTED INTO THE GLOBAL ANALYSIS AND FORECAST SYSTEM
/BOTH AVN AND MRF RUNS/...THE T170L42 SYSTEM IMPLEMENTED IN JUNE
1998 AND UPDATED IN JULY 1998 HAS NOT PERFORMED AS EXPECTED AND
LIMITED COMPUTER RESOURCES PRECLUDE TESTING ANY POTENTIAL
IMPROVEMENTS...HORIZONTAL AND VERTICAL RESOLUTIONS ARE REDUCED TO
PRE-JUNE 1998 VALUES /T126 AND 28 LAYERS/...ADJUSTMENTS TO THE
ANALYSIS SYSTEM PRODUCE INITIAL DATA FIELDS CLOSER TO
OBSERVATIONS...CHANGES TO PHYSICAL PARAMETERIZATIONS MADE IN
JUNE/JULY 1998 ARE RETAINED /SEE TPB 449/...THE MRF FORECAST
SYSTEM CONSISTS OF A T126L28 FORECAST TO 168 HOURS...AND T62L28
THEREAFTER...TESTING SHOWS MARKED IMPROVEMENT IN TROPICAL SYSTEMS
AND CONSISTENT SUPERIORITY OVER THE OPERATIONAL MODEL USING
TRADITIONAL SCORING METHODS...ON-LINE DOCUMENTATION OF THE
CHANGES IS AVAILABLE AT HTTP://WWW.NWS.NOAA.GOV/OM/TPBPR.HTM
/NUMBER 450/.../USE LOWER CASE FOR URL/...ROUTINE MONITORING OF
THE EFFECT OF THESE CHANGES WILL CONTINUE AND FUTURE MODEL
ADJUSTMENTS WILL BE MADE WHERE NECESSARY.
END
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