973  
FXUS10 KWNH 110708  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
307 AM EDT TUE AUG 11 2020  
 
VALID AUG 11/0000 UTC THRU AUG 14/1200 UTC  
 
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND  
FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...LONGWAVE TROUGHING OVER THE NORTHWEST TO THE NORTHERN PLAINS  
TUESDAY THROUGH THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF/00Z GEFS MEAN  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
DURING TUESDAY THROUGH THURSDAY, THE MODEL CONSENSUS IS FOR A  
LONGWAVE TROUGH TO AMPLIFY ACROSS THE PACIFIC NORTHWEST INTO  
NORTHERN CA. LOW AMPLITUDE SHORTWAVES EJECT AND MOVE EAST  
NORTHEAST ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS. ON THU  
NIGHT THE MODELS SHIFT THE TROUGH AXIS EAST ACROSS THE NORTHERN  
ROCKIES AND HIGH PLAINS. MINOR TIMING DIFFERENCES DEVELOP, WITH  
THE OPERATIONAL GFS FASTER THAN OTHER MODELS. AS USUAL, THE GEFS  
MEAN HAD SLOWER FORWARD PROGRESSION THAN THE OPERATIONAL GFS AND  
IS PREFERRED, GIVEN THE GFS BIAS OF MOVING LONGWAVE TROUGHS TOO  
QUICKLY.  
 
MID TO UPPER MS VALLEY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF/00Z GFS  
CONFIDENCE: AVERAGE  
 
THE DIFFERENCES NOTED WERE THE 12Z UKMET/CMC/00Z NAM/00Z ECMWF  
SHOWED CONVECTIVELY GENERATED VORTICITY MAXIMA THAT RESULTED IN  
POTENTIALLY SPURIOUS CLOSED LOWS WITHIN PROGRESSIVE WAVES EJECTING  
NORTHEAST ACROSS THE UPPER MS VALLEY (UKMET OVER IA, NAM OVER MO  
THU NIGHT)). THE 00Z GFS ALLOWED FOR A LESS DEVELOPED AND FASTER  
MOVING LOW, WHICH APPEARS TO BE A TREND ON THE RIGHT DIRECTION.  
 
SOUTHEAST TO MID ATLANTIC  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF/21Z SREF MEAN  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS SHOW A HIGH AMPLITUDE RIDGE OVER THE WESTERN ATLANTIC  
THAT KEEPS A MID LEVEL TROUGH OVER THE EASTERN CAROLINAS AND  
GEORGIA IN PLACE OR DRIFTING SLOWLY. THIS RESULTS IN INCREASED  
AGREEMENT OVER PRIOR FORECASTS. WITH GOOD AGREEMENT AMONG THE  
ECMWF AND GFS, ALONG WITH THE ENSEMBLE MEANS OF THE 21Z SREF/12Z  
ECMWF MEAN, AND 18Z GEFS MEAN, A CONSENSUS OF THESE SOLUTIONS  
WOULD RESOLVE MINOR TIMING/AMPLITUDE DIFFERENCES.  
 
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  
 
PETERSEN  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page