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575
NOUS41 KWBC 031954
PNSNMC
NATIONAL TECHNICAL INPLEMENTATION MESSAGE 97-29
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
300 PM EST MON NOV 3 1997
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: SMALL CHANGES TO THE NCEP GLOBAL ANALYSIS/FORECAST
SYSTEM...EFFECTIVE NOV 05 1997
BEGINNING WITH THE 12Z GLOBAL MODEL RUN ON NOV 05 1997...A SET OF
SMALL CHANGES WILL BE IMPLEMENTED INTO THE GLOBAL ANALYSIS AND
FORECAST SYSTEM (BOTH AVN AND MRF RUNS)...CAREFUL EVALUATION OF
THE IMPACT OF THESE CHANGES ON THE FORECAST SYSTEM AT T126
RESOLUTION SHOWS THAT A FORECASTER WILL SEE LITTLE DIFFERENCE...
THIS EVALUATION WAS SUBJECTIVE (MEDIUM-RANGE AND INTERNATIONAL
DESKS AT NCEP) AS WELL AS OBJECTIVE...RESULTS ARE PUBLISHED IN A
TECHNICAL PROCEDURES BULLETIN...WHICH MAY BE VIEWED ON NCEP/EMC
HOMEPAGE AT HTTP://NIC.FB4.NOAA.GOV:8080/RESEARCH/GLOBAL2.HTML...
CLICK ON RECENT TPB'S)...CHANGES ARE LISTED HERE:
(1) ANALYSIS
A. NEW OBSERVATION ERROR TABLE...
B. BETTER ASSIMILATION OF SATELLITE (HIRS) DATA...DECREASES
100-300MB TEMPERATURE BIAS...
C. NEW DATA SOURCES...PROFILER...ASDAR...METAR...ERS-2
WINDS...ETC
(2) MODEL
A. MOISTURE DIFFUSION ADJUSTMENT...REDUCES TENDENCY TO
PRODUCE WAVELIKE PATTERNS OF LIGHT PRECIPITATION IN MOUNTAINOUS
TERRAIN OF ARCTIC AIR MASSES...
B. SOIL MOISTURE NUDGED TO CLIMATOLOGY...PREVENTS
SIGNIFICANT DEPARTURES OF SOIL MOISTURE FROM CLIMATOLOGY IN
EXTENDED RUNS...
C. CONSERVATION OF DRY MASS...REMOVES GLOBAL MEAN SURFACE
PRESSURE LOSS OF SEVERAL MB/YEAR IN EXTENDED RUNS
(3) OUTPUT DATA
A. PRESSURE GRIB DATA AT 50MB VERTICAL RESOLUTION...
ADDS 10 NEW PRESSURE LEVELS TO THE AVN OUTPUT AT 0...12...24...36
FORECAST HOURS...
B. MODEL CONVECTIVE CLOUD AMOUNT/BASE/TOP...LOCATED IN
SURFACE FLUX FILES
END
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