19990514:RUC changes

• To: nws-changes@xxxxxxxxxxxxxxxx
• Subject: 19990514:RUC changes
• From: Linda Miller <lmiller@xxxxxxxxxxxxxxxx>
• Date: Fri, 14 May 1999 11:20:16 -0600

999 
NOUS41 KWBC 141624
PNSWSH
 
PUBLIC INFO. STATEMENT...TECHNICAL IMPLEMENTATION NOTICE 99-09
NATIONAL WEATHER SERVICE HEADQUARTERS WASHINGTON DC
1220 PM EDT FRI MAY 14 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.
          
A RELATIVELY SMALL SET OF CHANGES FOR THE RAPID UPDATE
CYCLE (RUC) WAS IMPLEMENTED ON THURSDAY MAY 6 FOR THE
1200 UTC RUN.  THESE CHANGES ARE FOR POST-PROCESSING AND
TO SWITCH TO DIFFERENT FORMAT FIXED FIELDS (VEGETATION
FRACTION AND SNOW/ICE COVER).  A CHANGE TO THE SPEED OF
RUC PROCESSING HAS ALREADY BEEN MADE AND IS DISCUSSED BELOW.      
    
          
------
THE CODE CHANGES INCLUDE
 - A BUG FIX AND CONSISTENCY CHANGES TO THE SURFACE TEMPERATURE
     AND DEWPOINT DIAGNOSIS FROM RUC NATIVE LEVELS
 - A CAPE/CIN CHANGE
 - MORE SMOOTHING OF ISOBARIC LEVEL WINDS
 - USE OF DIFFERENT ICE AND VEGETATION FRACTION FIELDS
 - GRIB IDENTIFIER CHANGES
-------
 
EFFECTS:
-------
 
-- IMPROVED DIAGNOSIS OF SURFACE TEMPERATURE AND DEWPOINT TEMP.  
  BACKGROUND: THE RUC SURFACE TEMPERATURE AND SURFACE DEWPOINT
FIELD ARE DIAGNOSED FROM THE RUC NATIVE LEVELS USING ITS
LOW-LEVEL LAPSE RATES TO A TOPOGRAPHY GRID THAT IS CLOSER TO
ACTUAL METAR ELEVATIONS.  THIS HAS BEEN DONE WITH BOTH THE RUC1
AND RUC2 SYSTEMS.  WITH THE FIXES...BIASES OF RUC2 ANALYZED
SURFACE TEMPERATURE AND DEWPOINT COMPARED TO ACTUAL METAR
OBSERVATIONS ARE REDUCED FROM 2 DEG C TO 0 IN THE WESTERN
US...AND STANDARD DEVIATION DIFFERENCES ARE REDUCED FROM ABOUT 2
DEG C TO ABOUT 1.4 DEG C. BIASES AND STANDARD DEVIATION ERRORS IN
RUC2 SFC FORECASTS ARE ALSO REDUCED. THESE IMPROVEMENTS ALSO
BENEFIT THE LIFTED INDEX CALCULATIONS.
  
-- THE DIAGNOSIS OF CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE)
HAS BEEN MODIFIED TO BETTER DETECT POTENTIAL FOR ELEVATED 
CONVECTION BY CONSIDERING CLOUD PARCELS IN THE LOWEST 300 MB NEAR
THE SURFACE...RATHER THAN THE PREVIOUS 180 MB THICK LAYER.  THIS
CHANGE WAS REQUESTED BY THE STORM PREDICTION CENTER.
 
-- ADDITIONAL SMOOTHING OF RUC ISOBARIC WIND FIELDS IN THE LOWER
TROPOSPHERE AND AT THE TROPOPAUSE IMPROVES THEIR ACCURACY.  THIS
MODIFICATION IS ONLY IN THE POST-PROCESSING...NOT IN THE MODEL OR
ANALYSIS.
 
-- THE ICE COVER FIELD FROM THE NESDIS SNOW/ICE ANALYSIS IS MORE
PRECISE THAN THE PREVIOUS ICE FIELD USED IN THE RUC.  THIS NESDIS
ICE FIELD WAS ALREADY USED THIS PAST WINTER WITH THE ETA.
 
-- THE USE OF A GRIB-BASED VEGETATION FRACTION FIELD HAS NO
EFFECT ON THE RUC OUTPUT.  IT NOW READS FROM A COMPRESSED
FORMAT...AND IS STILL THE NESDIS AVHRR-BASED 0.14 DEG MONTHLY
GREENNESS FRACTION ALSO USED BY THE ETA.
 
-- GRIB IDENTIFIER CORRECTIONS:
    NUMBER CONCENTRATION FOR ICE PARTICLES FROM 180 TO 198
    SURFACE RUNOFF                         FROM 234 TO 235
    SUB-SURFACE RUNOFF                     FROM 198 TO 234
 
SPEED OF RUC & ETA PROCESSING IMPROVED
--------------------------------
 
AS OF 28 APRIL 1999...NCEP ALLOCATED 10 PROCESSORS ON THE CRAY
FOR ALL RUNS OF THE RUC2 AS PART OF IMPROVING THE USE OF THE CRAY
FOR THE OVERALL NCEP MODEL SUITE.
 
THE EFFECTS OF THIS CHANGE ARE THAT RUC FORECAST GRIDS OUT TO 12H
AT 0300...0600...0900...1500...1800...AND 2100 UTC ARE AVAILABLE
ABOUT 25-30 MIN EARLIER THAN PREVIOUSLY.  ANALYSES AT ALL TIMES
ARE AVAILABLE ABOUT 5-8 MIN EARLIER NOW...AND FORECASTS OUT TO 3H
AT NON-3-HOURLY TIMES ARE AVAILABLE ABOUT 15 MIN SOONER.  
 
THIS CHANGE REDUCES THE CONFLICT BETWEEN RUC2 AND ETA RUNS SUCH
THAT THE ETA RUNS ARE ALSO AVAILABLE 10-15 MINUTES EARLIER.
 
----------
IF YOU HAVE FURTHER QUESTIONS...CONTACT THE RUC WEB FORUM AT
HTTP://MAPS.FSL.NOAA.GOV/FORUM/EVAL (LOWER CASE)
OR CONTACT
 
STAN BENJAMIN
NOAA/FORECAST SYSTEMS LABORATORY
325 BROADWAY...R/E/FS1
BOULDER CO  80301
EMAIL: BENJAMIN/AT SIGN/FSL.NOAA.GOV
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