017  
FXUS10 KWNH 121854  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
253 PM EDT MON AUG 12 2019  
 
VALID AUG 12/1200 UTC THRU AUG 16/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GEFS MEAN/00Z ECENS MEAN  
CONFIDENCE: BELOW AVERAGE  
 
THE SYNOPTIC EVOLUTION THROUGH THE FORECAST PERIOD IS GENERALLY  
WELL AGREED UPON BY THE GLOBAL SUITE, BUT SMALLER SCALE FEATURES  
CREATE DISCREPANCIES IN THE SENSIBLE WEATHER AND SYNOPTIC  
EVOLUTION LEADING TO A LOWER THAN AVERAGE CONFIDENCE FORECAST.  
 
THE UKMET CONTINUES TO OCCASIONALLY BE SOMEWHAT OF A STRONGER  
OUTLIER WITH ITS RIDGING ACROSS THE SOUTHERN U.S. THROUGH THE  
PERIOD, BUT THE GUIDANCE DOES ALL AGREE ON GRADUALLY ADVANCING A  
PORTION OF THE RIDGING WESTWARD INTO THE SOUTHWEST. MEANWHILE, A  
SERIES OF RELATIVELY LOW-AMPLITUDE SHORTWAVES WILL ADVANCE ACROSS  
THE MIDWEST, GREAT LAKES AND INTO THE EAST THROUGH THE PERIOD  
WHICH WILL CARVE OUT A BROAD LONGWAVE TROUGH INVOLVING MUCH OF THE  
NORTHERN AND EASTERN U.S. THE NAM OVERALL IS A LITTLE STRONGER  
THAN THE MODEL CONSENSUS WITH THE SHORTWAVE ENERGY, AND THE UKMET  
IS ON THE WEAKER SIDE. THE GFS, CMC AND ECMWF ARE CLUSTERED IN  
BETWEEN.  
 
ALL OF THE MODELS ALLOW A COLD FRONT TO ADVANCE THROUGH THE  
MIDWEST AND INTO THE EAST OVER THE NEXT FEW DAYS, AND THE MODELS  
HAVE COME INTO A BIT BETTER AGREEMENT WITH THE 12Z CYCLE AS THE  
ECMWF AND CMC HAVE TRENDED A LITTLE FARTHER SOUTH TOWARD THE NAM  
AND GFS CAMP BY THE END OF THE PERIOD AS THE FRONT STALLS OVER  
PORTIONS OF THE MID-ATLANTIC AND SOUTHEAST. OVERALL, THE UKMET  
PROBABLY HAS ITS FRONT A TAD TOO FAR SOUTH, BUT THE DIFFERENCE IS  
RATHER MODEST COMPARED TO THE MODEL CONSENSUS. ALL OF THE MODELS  
ALSO HAVE AN ELONGATED AREA OF LOW PRESSURE FOCUSED ALONG THE  
FRONT OVER THE SOUTHEAST, ALONG WITH A SEPARATE WEAK LOW CENTER  
OVER THE OH VALLEY. THE NAM APPEARS TO BE PERHAPS A TAD STRONGER  
WITH THIS OH VALLEY LOW COMPARED TO THE GLOBAL MODELS, BUT THIS  
APPEARS TO BE RELATED TO THE NAM HAVING SLIGHTLY STRONGER HEIGHT  
FALLS.  
 
THERE IS ALSO SPREAD ACROSS THE NORTHWEST BY THE END OF THE PERIOD  
AS THE GUIDANCE FAVORS A SHORTWAVE TROUGH DROPPING IN TOWARD THE  
PACIFIC NORTHWEST. THE GFS AND UKMET ARE THE MOST PROGRESSIVE WITH  
THE CMC THE SLOWEST.  
 
BASED ON THE MODEL SPREAD IN THE DETAILS OF THE ENERGY IN THE  
NORTHWEST AND TO SOME MODEST EXTENT ALONG THE EAST COAST BY THE  
END OF THE PERIOD, A BLEND OF THE ENSEMBLE MEANS WILL BE PREFERRED  
WHICH ARE IN REASONABLY GOOD AGREEMENT ACROSS MOST OF THE CONUS.  
ALTHOUGH IT IS NOTED THAT THE 00Z ECENS MEAN IS A BIT STRONGER  
THAN THE MOST OF THE DETERMINISTIC MODELS AND THE 12Z GEFS MEAN  
ACROSS THE NORTHWEST AT THE END OF THE PERIOD.  
 
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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