879  
FXUS10 KWNH 080657  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
256 AM EDT SAT AUG 8 2020  
 
VALID AUG 8/0000 UTC THRU AUG 11/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S.  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND THROUGH 12Z SUNDAY, THEN  
ECMWF/GFS/CMC  
CONFIDENCE: AVERAGE  
 
7Z UPDATE: THE 00Z NAM IS SLOWER AND CONSIDERABLY STRONGER WITH  
THE SHORTWAVE CROSSING THE NORTHERN PLAINS AND UPPER MIDWEST ON  
MONDAY COMPARED TO ALL OF THE OTHER 00Z GUIDANCE. THE ECMWF  
TRENDED SLIGHTLY STRONGER WITH THE UPPER RIDGE ACROSS THE MIDWEST  
AND THE OHIO VALLEY AND IN LINE WITH THE UKMET. OTHERWISE, NO  
MAJOR CHANGES NOTED WITH THE ARRIVAL OF THE FULL 00Z MODEL SUITE.  
 
----------  
THE OVERALL WEATHER PATTERN ACROSS THE CONTINENTAL U.S. WILL BE  
QUASI-ZONAL ACROSS THE NORTHERN TIER STATES ON SATURDAY WITH A  
BUILDING UPPER RIDGE CENTERED OVER THE SOUTHERN PLAINS REGION. A  
WEAK TROUGH AXIS OVER THE MID-ATLANTIC REGION AND THE NORTHEAST  
U.S. WILL CONTINUE TO SLOWLY EMERGE OFFSHORE FOLLOWED BY LOW  
AMPLITUDE RIDGING ALOFT. THERE WILL ALSO BE A BROAD, POSITIVELY  
TILTED TROUGH AXIS STRETCHED ACROSS THE INTERMOUNTAIN WEST AND  
EXTENDING ACROSS CALIFORNIA. THE MAIN WEATHER FEATURE WILL BE AN  
EVOLVING CLOSED LOW OVER SOUTH-CENTRAL CANADA WITH MULTIPLE  
SHORTWAVE PERTURBATIONS ROTATING AROUND ITS SOUTHERN PERIPHERY,  
AND THESE SHORTWAVES WILL SUSTAIN COLD FRONTAL PASSAGES ACROSS THE  
NORTH-CENTRAL U.S. THROUGH MONDAY.  
 
THERE IS ENOUGH DETERMINISTIC MODEL AGREEMENT THROUGH 12Z SUNDAY  
TO MERIT THE USE OF A GENERAL MODEL COMPROMISE. BEYOND THAT, THE  
00Z NAM BECOMES A BIT MORE AMPLIFIED WITH THE UPPER LOW ACROSS  
SASKATCHEWAN AND MANITOBA, AND SLOWER WITH THE SHORTWAVE CROSSING  
THE NORTHERN PLAINS BY MONDAY. THE GFS IS MORE POTENT WITH THE  
LEADING SHORTWAVE ACROSS THE UPPER MIDWEST BY MONDAY MORNING. THE  
12Z UKMET IS A LITTLE STRONGER WITH THE UPPER LEVEL RIDGE ACROSS  
THE OHIO VALLEY BY THE END OF THE FORECAST PERIOD. TAKING THESE  
FACTORS INTO ACCOUNT, USING A 12Z ECMWF/GFS/CMC BLEND AS A MASS  
FIELD STARTING POINT SHOULD WORK WELL.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:  
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.  
PDF  
 
HAMRICK  
 

 
 
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