980707: Model Changes

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 980707: Model Changes
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Tue, 7 Jul 1998 15:02:14 -0600 (MDT)

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NATIONAL TECHNICAL IMPLEMENTATION MESSAGE 98-13
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
400 PM EDT TUE JUL 7 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:  MULTIPLE CHANGES TO THE NCEP GLOBAL ANALYSIS/FORECAST
          SYSTEM...EFFECTIVE JUN 15 1998

BEGINNING WITH THE 12Z GLOBAL MODEL RUN ON JUN 15 1998...MULTIPLE
CHANGES WERE IMPLEMENTED INTO THE GLOBAL ANALYSIS AND FORECAST
SYSTEM /BOTH AVN AND MRF RUNS/...A MAJOR CHANGE IS INCREASED
RESOLUTION...WHERE T126 HORIZONTAL RESOLUTION BECOMES T170 AND 28
VERTICAL LAYERS BECOME 42...HOWEVER FOR COMPUTATIONAL REASONS...
THE HORIZONTAL RESOLUTION IN MRF FORECASTS IS REDUCED TO T126 AND
T62 AFTER 84 AND 168 HOURS RESPECTIVELY...AND VERTICAL RESOLUTION
IS REDUCED TO 28 LAYERS BEYOND 84 HOURS...ON-LINE DOCUMENTATION
OF THE CHANGES ARE FOUND IN A DRAFT TECHNICAL PROCEDURES BULLETIN
AT HTTP://WWW.NWS.NOAA.GOV/OM/TPB/INDDRAFT.HTM  /USE LOWER CASE/.
THE BULLETIN IS NUMBER 449.   FORECASTERS WILL SEE IMPROVED
MAINTENANCE OF JET CORES /REDUCED RMS VECTOR ERRORS/...WARMER
TEMPERATURES /ESPECIALLY IN TROPICS/...AND BETTER PRECIPITATION
BIAS FOR BOTH SMALL AND LARGE AMOUNTS... HOWEVER THERE IS A WARM
BIAS AT LOW LEVELS OVER LAND...THERE CONTINUES TO BE A TENDENCY
FOR SPURIOUS TROPICAL SYSTEMS TO DEVELOP IN THE FORECAST...WHICH
IS PARTIALLY DUE TO THE HIGHER RESOLUTION ...THE PROBLEM AREAS
WILL BE ROUTINELY MONITORED AND FUTURE MODEL ADJUSTMENTS WILL BE
MADE WHERE NECESSARY...MAJOR CHANGES IN THE ANALYSIS AND FORECAST
MODEL ARE LISTED BELOW:

/1/ ANALYSIS
  A. T170...42 LAYERS
    B. IMPROVED USE OF POLAR ORBITER DATA
    C. INCLUSION OF GOES DATA /NEW/
    D. REFORMATTED BACKGROUND ERROR COVARIANCE
    E. 3-D OZONE ANALYSIS /NEW/
 /2/ MODEL
    A. T170...42 LAYERS
    B. MORE ACCURATE SHORTWAVE RADIATION
    C. PROGNOSTIC OZONE /NEW/
    D. GRAVITY WAVE DRAG ENHANCEMENT
    E. CONVECTION AND LAND SURFACE ENHANCEMENTS                   
            
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