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870
NOUS41 KWBC 301926
PNSWSH
PUBLIC INFO. STATEMENT...TECHNICAL IMPLEMENTATION NOTICE 99-11
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
330 PM EDT FRI JUL 30 1999
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 NATIONAL CENTER FOR ENVIRONMENTAL
PREDICTION /NCEP/ RAPID UPDATE CYCLE ANALYSIS/FORECAST
SYSTEM LAST MONDAY JULY 26 1999.
TWO FIXES WERE MADE TO FIX ERRORS IN THE MOISTURE FIELDS USED IN
THE RAPID UPDATE CYCLE (RUC) BOUNDARIES. THESE CHANGES WERE
IMPLEMENTED AT 15Z MONDAY 26 JULY 1999. THE PRIMARY
ERROR IS THAT SATURATION VAPOR PRESSURE IS CALCULATED USING
VIRTUAL TEMPERATURE RATHER THAN TEMPERATURE. THE SECOND ERROR IS
THAT THE SATURATION VAPOR PRESSURE AT TEMPERATURES BELOW -15 DEG
C IS CALCULATED WITH RESPECT TO ICE INSTEAD OF WATER. THE IMPACT
OF THE FIXES TO THESE ERRORS IS TO ELIMINATE MUCH OF THE
ERRONEOUS PRECIPITATION ALONG THE RUC BOUNDARIES OVER WARM OCEANS
AND SLIGHTLY REDUCE SOME OF THE EXCESSIVE AREAL COVERAGE OF RUC
PRECIPITATION OVER WARM OCEANS.
EXAMPLES OF 12-H RUC PRECIPITATION BEFORE AND AFTER THE CHANGE
MAY BE VIEWED AT
HTTP://MAPS.FSL.NOAA.GOV/RUC_BC_FIX.HTML (LOWER CASE)
IF YOU HAVE QUESTIONS...CONTACT THE RUC WEB FORUM AT
HTTP://MAPS.FSL.NOA.GOV/FORUM/EVAL (LOWER CASE)
OR CONTACT
STAN BENJAMIN
NOAA/FORECAST SYSTEMS LABORATORY
325 BROADWAY R/E/FS1
BOULDER CO 80301
EMAIL: BENJAMIN@xxxxxxxxxxxx
PHONE: (303) 497-6387
OR
GEOFF MANIKIN
NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION ENVIRONMENTAL
MODELING CENTER
5200 AUTH ROAD
CAMP SPRINGS MD 20746-4304
PHONE: (301) 763-8000 EXT 7263
END
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