458  
FXUS10 KWNH 130832  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
431 AM EDT THU AUG 13 2020  
 
VALID AUG 13/0000 UTC THRU AUG 16/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z PRELIMINARY MODEL EVALUATION INCLUDING PREFERENCES AND  
FORECAST CONFIDENCE  
 
...LONGWAVE TROUGH MOVING FROM THE NORTHWEST TO THE WESTERN GREAT  
LAKES...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GEFS/ECENS/NAM/CMC BLEND  
CONFIDENCE: AVERAGE  
 
AN UPPER LEVEL TROUGH WITH AN EMBEDDED STRENGTHENING VORT MAX  
DIGGING THROUGH ITS BASE WILL MOVE FROM THE NW THROUGH THE WESTERN  
GREAT LAKES BY SATURDAY. THE KEY FEATURE HERE IS THAT VORT MAX  
WHICH MAY SPAWN A WAVE OF LOW PRESSURE AND WILL DRAG A COLD FRONT  
EASTWARD BENEATH IT. OTHER THAN THE GFS, WHICH IS A BIT FAST, THE  
TIMING ENVELOPE IS SMALL AMONG THE GLOBAL MODELS. HOWEVER, THE  
ECMWF IS A SHALLOW SOLUTION COMPARED TO THE OTHER SOLUTIONS, WHILE  
THE UKMET PRODUCES QPF WHICH IS QUITE A BIT HIGHER THAN ANY OTHER  
SOLUTION. A COMPROMISE OF THE GEFS/ECENS/NAM/CMC LEAVES A  
REASONABLE SOLUTION FOR THE PROGRESSION AND AMPLITUDE OF THIS  
FEATURE, WITH HEAVY RAINFALL POSSIBLE ACROSS THE UPPER MIDWEST  
ASSOCIATED WITH THIS TROUGH.  
 
...LARGE TROUGH DEVELOPING ACROSS THE EASTERN CONUS THROUGH  
SUNDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GEFS/ECENS/SREF/CMC  
CONFIDENCE: BELOW AVERAGE  
 
AN UPPER LEVEL TROUGH WILL GRADUALLY ENVELOP THE ENTIRE EASTERN  
CONUS, WHILE A SHORTWAVE RIDGE BLOSSOMS INTO SOUTHERN CANADA. THIS  
LEAVES A WEAKNESS IN THE HEIGHT FIELDS ACROSS THE OHIO VALLEY INTO  
WHICH A SECONDARY TROUGH OR EVEN A CLOSED LOW MAY DEVELOP  
SATURDAY. THERE CONTINUES TO BE QUITE A BIT OF SPREAD IN BOTH THE  
AMPLITUDE OF THIS TROUGH, AND POSITION/INTENSITY OF THE MID-LEVEL  
WAVE/CLOSED LOW DEVELOPING IN THE OHIO VALLEY. THERE ARE ALSO  
SIGNIFICANT DIFFERENCES WHICH ARISE BY SATURDAY ACROSS NEW ENGLAND  
OWING TO THE POSITION OF THE SHORTWAVE RIDGE AND ITS INTERACTION  
WITH THE OH VLY FEATURE. THE DETERMINISTIC MODELS ARE ALL OVER THE  
PLACE, BUT THE GEFS/SREF MEANS SUGGEST A RATHER SIMILAR EVOLUTION  
SO ARE WEIGHTED HEAVILY IN THE BLEND. DESPITE BEING MORE SHALLOW,  
THE ECENS HAS SHOWN DECENT CONSISTENCY, AND OF THE DETERMINISTIC  
MODELS THE CMC IS THE ONE WHICH MOST CLOSELY RESEMBLES THE  
PREFERENCES FROM THE MEANS. HOWEVER, AT THIS TIME THERE REMAINS  
BELOW AVERAGE CONFIDENCE, AND WHILE A TROUGH ACROSS THE EAST SEEMS  
LIKELY, ITS INTENSITY, AND WHERE THE SECONDARY LOW MAY DEVELOP TO  
ENHANCE RAINFALL POTENTIAL, REMAIN QUITE UNCERTAIN.  
 
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  
 
WEISS  
 

 
 
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