583   
FXUS10 KWNH 240446  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1246 AM EDT TUE SEP 24 2019  
  
VALID SEP 24/0000 UTC THRU SEP 27/1200 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
00Z PRELIMINARY MODEL EVALUATION WITH PREFERENCES AND FORECAST  
CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..CONUS  
  
~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 12Z CMC/18Z GEFS  
CONFIDENCE: ABOVE AVERAGE  
  
THE GUIDANCE IS IN EXCEPTIONALLY GOOD AGREEMENT IN THE LONGWAVE  
PATTERN ACROSS THE CONUS THE NEXT 3 DAYS. A LARGE CLOSED LOW OVER  
THE HUDSON BAY, CANADA, WILL SHED VORTICITY IMPULSES ACROSS THE  
NORTHERN TIER IN A FAST NORTHERN STREAM THROUGH LATE WEEK. FURTHER  
SOUTH, A GENERAL FLAT RIDGE WILL ENCOMPASS MUCH OF THE REGION FROM  
35N LATITUDE AND SOUTH, THE EXCEPTION BEING A SLOW MOVING CLOSED  
LOW DROPPING THROUGH THE SOUTHWEST AND INTO MEXICO BEFORE  
RETURNING TO THE NORTHEAST AND SLOWLY BECOMING ABSORBED INTO THE  
WESTERLIES FRIDAY MORNING.  
  
FOR THE SOUTHWEST CLOSED LOW, THERE IS LITTLE SPREAD WHATSOEVER  
UNTIL THE END OF DAY 3 WHEN THE UKMET OUTPACES THE REMAINING  
GUIDANCE IN ITS ABSORPTION INTO THE FAST FLOW TO THE NORTH. THE  
DIFFERENCE IN TIMING AND SPEED IS MINIMAL EVEN BY DAY 3, SO A  
GENERAL MODEL BLEND IS SUFFICIENT. HOWEVER, FURTHER EAST, A  
SHORTWAVE DRIVING A COLD FRONT ACROSS THE MIDDLE OF THE COUNTRY  
AND THEN INTO THE EAST COAST D2-3 BEGINS TO FEATURE MORE  
UNCERTAINTY AS THE CMC AND GEFS MEAN SLOW THE PROGRESSION TO  
BECOME WELL WEST OF THE MEAN TROUGH AXIS BY FRIDAY MORNING. THIS  
SEEMS TO BE DUE TO A WEAKER AND MORE STRONGLY KINKED 250MB JET  
STREAK IN THE VICINITY OF THE GREAT LAKES. WHILE THE GEFS AND CMC  
ARE ACTUALLY IN PRETTY GOOD AGREEMENT, THEY ARE MUCH SLOWER THAN  
THE GLOBAL CONSENSUS, AND WITH A FAST NORTHERN STREAM ANTICIPATE  
THE FASTER SOLUTIONS ARE MORE LIKELY.  
  
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
WEISS  
  
  
 
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