861  
FXUS10 KWNH 231834  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
133 PM EST FRI FEB 23 2018  
 
VALID FEB 23/1200 UTC THRU FEB 27/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..SURFACE WAVE CROSSING THE GREAT LAKES/NORTHERN NEW ENGLAND
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN GOOD AGREEMENT WITH THE EJECTING THE SURFACE  
WAVE CURRENTLY CROSSING THE GREAT LAKES REGION THAT WILL CLIP  
PORTIONS OF NORTHERN NEW ENGLAND TONIGHT. A GENERAL MODEL  
ORIENTATION OF THE SURFACE FRONT ACROSS THE SOUTH THIS PERIOD, AND  
ALSO WITH THE DETAILS OF THE SURFACE WAVE LIFTING UP ACROSS UPPER  
MISSISSIPPI VALLEY AND GREAT LAKES. A GENERAL MODEL BLEND WILL BE  
PREFERRED.  
 
   
..STRONG SHORTWAVE OVER THE FOUR CORNERS REGION TODAY
 
   
..CYCLOGENESIS OVER THE PLAINS AND LIFTING TO THE MIDWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS, 12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS TAKE A STRONG SHORTWAVE TROUGH DIGGING DOWN ACROSS THE  
FOUR CORNERS REGION TODAY AND EJECT IT OUT ACROSS THE PLAINS ON  
SATURDAY WHERE WELL-DEFINED CYCLOGENESIS WILL OCCUR. AN UPPER  
TROUGH WILL THEN LIFT NORTHEAST ACROSS THE UPPER MIDWEST BY  
SATURDAY NIGHT AND TAKE ON A NEGATIVE TILT WHICH WILL HELP TO  
DEEPEN SURFACE LOW PRESSURE AS IT LIFTS ACROSS THE UPPER GREAT  
LAKES REGION BY EARLY SUNDAY. THE 12Z NAM ENDS UP AGAIN STRONGER  
ALOFT WITH ITS ENERGY TRAVERSING THE UPPER MIDWEST AND PLACES ITS  
SURFACE LOW NORTHWEST OF THE MODEL CONSENSUS AS IT NEARS THE UPPER  
MIDWEST AND UPPER GREAT LAKES. THE 12Z CMC ALSO IS A BIT DEEPER  
ALOFT LIKE THE NAM. HOWEVER, THE 12Z GFS, 12Z UKMET AND 12Z ECMWF  
ARE NOT AS STRONG WITH THE HEIGHT FALLS, BUT NEVERTHELESS SHOW AN  
ENERGETIC AND NEGATIVELY TILTING UPPER TROUGH WITH A RATHER STRONG  
SURFACE LOW. THE GFS, UKMET AND ECMWF SHOW GOOD MODEL CLUSTERING  
AND ENSEMBLE SUPPORT, AND SO A BLEND OF THESE SOLUTIONS WILL BE  
PREFERRED.  
 
   
..SHORTWAVE ARRIVING OVER THE PACIFIC NORTHWEST ON SATURDAY
 
   
..CROSSING THE FOUR CORNERS/HIGH PLAINS ON SUNDAY
 
   
..EJECTING EAST ACROSS THE MISSISSIPPI/OHIO VALLEYS ON MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE NEXT IN A SERIES OF SHORTWAVES TO DROP SOUTHEAST DOWN ACROSS  
WESTERN NORTH AMERICA AND INTO THE PACIFIC NORTHWEST WILL ARRIVE  
ON SATURDAY AND THEN RAPIDLY DROP DOWN INTO THE FOUR CORNERS  
REGION ON SUNDAY BEFORE RAPIDLY EJECTING EAST TOWARD THE MID  
MISSISSIPPI VALLEY AND OHIO VALLEY ON MONDAY. THE MODELS ARE IN  
GOOD AGREEMENT WITH THEIR MASS FIELD DETAILS OF THIS SYSTEM UNTIL  
SUNDAY WHEN THE 12Z UKMET BEGINS TO LAG THE MODEL CONSENSUS JUST A  
TAD, AND THE 12Z GFS BEGINS TO OUTRUN IT SOMEWHAT. HOWEVER, THE  
LATEST GUIDANCE INCLUDING THE LATEST CMC AND ECMWF AND NAM ARE ALL  
CLUSTERED GENERALLY IN BETWEEN THE UKMET AND GFS WITH THE OVERALL  
SPREAD RATHER MINIMAL AT THIS POINT. THEREFORE, GIVEN THE IMPROVED  
MODEL CLUSTERING AND ENSEMBLE SUPPORT, A GENERAL MODEL BLEND WILL  
BE PREFERRED.  
 
   
..SHORTWAVE ARRIVING OVER THE PACIFIC NORTHWEST ON SUNDAY
 
   
..LARGER SCALE TROUGH EVOLUTION OVER THE WEST BY MONDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THE GUIDANCE BRINGS ANOTHER SHORTWAVE INTO THE PACIFIC NORTHWEST  
ON SUNDAY ALONG WITH A PROGRESSIVE COLD FRONT. THE GUIDANCE IS IN  
GOOD AGREEMENT WITH THE ARRIVAL OF THE SHORTWAVE ENERGY AND THE  
EVOLUTION OF THE HEIGHT FALLS DIGGING DOWN ACROSS CALIFORNIA AND  
THE GREAT BASIN ON MONDAY WHICH WILL LEAD TO A LARGER SCALE TROUGH  
EVOLUTION AIMING FOR THE SOUTHWEST. THE 12Z ECMWF ACTUALLY DID  
TREND A BIT STRONGER AND SUGGESTS A MID LEVEL LOW CENTER CLOSING  
OFF OVER CENTRAL CALIFORNIA BY LATE MONDAY FOR WHICH THERE IS SOME  
ENSEMBLE SUPPORT. OVERALL, THE MODEL MASS FIELD SPREAD IS  
RELATIVELY LOW AND SO A GENERAL MODEL BLEND WILL STILL BE  
MAINTAINED FOR THE TIME BEING.  
 
 
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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