545  
FXUS10 KWNH 091846  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
245 PM EDT THU APR 09 2020  
 
VALID APR 09/1200 UTC THRU APR 13/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..DEEP CYCLONE IMPACTING THE NORTHEAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
AN ANOMALOUSLY DEEP CLOSED LOW CROSSING THE GREAT LAKES WILL  
DEEPEN AND TAKE ON A NEGATIVE TILT AS IT APPROACHES THE NORTHEAST  
THIS AFTERNOON/EVENING. MEANWHILE, LOW PRESSURE CROSSING THE  
INTERIOR OF NY STATE AND NEW ENGLAND WILL CONSOLIDATE OVER COASTAL  
AREAS OF MAINE THIS EVENING AND DEEPEN INTO AN INTENSE LOW CENTER.  
THE 12Z GFS IS OVERALL A TAD DEEPER THAN THE 12Z NAM AND THE 12Z  
NON-NCEP SOLUTIONS. THE GFS ALSO TRACKS ITS SURFACE LOW A TAD  
FARTHER INLAND OVER MAINE VERSUS THE MORE CONCENTRATED LOW CENTER  
EVOLUTION ALONG THE MAINE COAST THAT THE REMAINING GUIDANCE  
FAVORS. THIS RESULTS IN THE GFS HAVING A SOMEWHAT STRONGER WARM  
NOSE WRAPPING FARTHER INLAND. THE PREFERENCE WILL BE TOWARD A  
NON-GFS BLEND AT THIS TIME.  
 
   
..SLOW-MOVING CLOSED LOW ACROSS THE SOUTHWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS GRADUALLY EJECT THE LARGE, SLOW-MOVING CUT-OFF SOUTHERN  
STREAM LOW OVER SOUTHERN CALIFORNIA OFF TO THE EAST OVER THE NEXT  
COUPLE OF DAYS. THE ENERGY IS EXPECTED TO OPEN UP INTO A  
PROGRESSIVE SHORTWAVE TROUGH OVER THE SOUTHERN PLAINS BY SATURDAY  
WHICH WILL THEN LIFT NORTHEAST AND GO NEGATIVE TILT OVER LOWER MS  
VALLEY AND MID-SOUTH BY SUNDAY AS IT COMES UNDER THE INFLUENCE OF  
STRONGER NORTHERN STREAM HEIGHT FALLS DROPPING DOWN OVER THE  
MIDWEST. THE 12Z GFS, JUST LIKE ITS PREVIOUS RUNS, CONTINUES TO BE  
THE FASTEST SOLUTION AS THE ENERGY EJECTS OUT ACROSS THE SOUTH.  
WITH ITS FASTER HEIGHT FALL PROGRESSION, THE GFS IS ALSO FASTER  
WITH ITS SURFACE FRONTAL PROGRESSION AND WAVE ACTIVITY, AND  
ACTUALLY ENDS UP WITH A SOMEWHAT STRONGER SURFACE LOW COMPARED TO  
THE OTHER MODELS BY SUNDAY. THE 12Z NON-NCEP MODELS DID TREND A  
TAD MORE PROGRESSIVE WITH THIS CYCLE (AT LEAST MASS FIELD WISE),  
BUT STILL TEND TO BE A LITTLE SLOWER THAN THE GFS. THE 12Z NAM  
OVERALL TENDS TO BE CLOSE TO THE MODEL CONSENSUS. GIVEN THE LATEST  
TRENDS, A MASS FIELD PREFERENCE TOWARD A NON-GFS BLEND WILL STILL  
BE MAINTAINED, BUT OVERALL AT LEAST GUIDANCE DOES CLUSTER TOGETHER  
A BIT BETTER.  
 
   
..UPPER LEVEL TROUGH/COLD FRONT REACHING THE NORTHWEST
 
   
..DROPPING THROUGH THE NORTHERN PLAINS/MIDWEST ON SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND...LED BY 12Z GEFS/00Z ECENS  
CONFIDENCE: AVERAGE  
 
SHORTWAVE ENERGY ALONG THE SOUTHERN COAST OF ALASKA WILL PROGRESS  
EASTWARD TO THE YUKON TERRITORY, AND WITH THE ACCELERATING/EXITING  
JET, THE UPSTREAM RIDGE WILL BREAK DOWN AND ALLOW FOR GREATER  
PROPAGATION EAST AND THEN SOUTHWARD ACROSS SOUTHWESTERN CANADA.  
THE HEIGHT-FALLS WILL OVERSPREAD THE LEE OF THE CANADIAN ROCKIES  
AND THEN THE NORTHERN HIGH PLAINS, AND SUPPORT A SURFACE COLD  
FRONT DROPPING SOUTHEASTWARD ACROSS THE NORTHERN PLAINS AND  
MIDWEST BY SUNDAY. THE 12Z NAM AND 12Z GFS BOTH TEND TO BE A  
LITTLE FASTER TO ADVANCE THEIR HEIGHT-FALLS TOWARD THE MIDWEST AND  
AS SUCH APPEAR TO BE A LITTLE FAST IN ADVANCING THE COLD FRONT  
DOWN TO THE SOUTHEAST. THE 12Z NON-NCEP SOLUTIONS ARE ALL JUST A  
TAD SLOWER. THE 00Z ECENS AND 12Z CMCE SUITES TEND TO FAVOR THE  
MODESTLY SLOWER CAMP, BUT THE 12Z GEFS IS A TAD FASTER. SO, BASED  
ON THE LATEST TRENDS, A GENERAL MODEL BLEND WEIGHTED TOWARD A  
BLEND OF THE 12Z GEFS MEAN AND 00Z ECENS MEAN WILL BE PREFERRED AS  
A COMPROMISE.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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