981104: Eta Model-NOUS (fwd)

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 981104: Eta Model-NOUS (fwd)
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Wed, 4 Nov 1998 07:50:35 -0700 (MST)

167 
NOUS41 KWBC 031604
PNSNMC
 
NATIONAL TECHNICAL IMPLEMENTATION MESSAGE 98-21
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
1100 AM EST TUE NOV 3 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 OPERATIONAL ETA MODEL
          SYSTEM...EFFECTIVE NOV 3 1998
 
AT 1200 UTC 03 NOVEMBER 1998 THE FOLLOWING CORRECTIONS TO THE 3-D
VARIATIONAL /3DVAR/ ANALYSIS USED IN THE 32-KM MESO ETA SYSTEM
WERE IMPLEMENTED:
 
- AN ERROR IN THE ORIGINAL 3DVAR CODE WHICH EXCLUDED MOST SURFACE
AND NEAR SURFACE DATA FROM BEING USED IN THE ANALYSIS WAS FIXED. 
THIS INCLUDES OBSERVATIONS OF PRESSURE...TEMPERATURE...MOISTURE
AND WIND.
 
- THE FOLLOWING STEPS WERE TAKEN TO IMPROVE THE FIT TO
OBSERVATIONS:
 
A/ THE VERTICAL CORRELATION LENGTH SCALE FOR MOISTURE WAS
INCREASED
 
B/ THE BACKGROUND ERROR VARIANCES WERE INCREASED BY 30-50
PERCENT.  THIS HAS THE EFFECT OF GIVING MORE WEIGHT TO THE
OBSERVATIONS AND LESS WEIGHT TO THE FIRST GUESS WHEN THE ANALYSIS
IS PERFORMED.
            
END