349  
FXUS10 KWNH 011846  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
145 PM EST THU MAR 01 2018  
 
VALID MAR 01/1200 UTC THRU MAR 05/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...ALONG WITH MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
   
..POWERFUL NOR'EASTER IMPACTING THE MID-ATLANTIC/NORTHEAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS HAVE COME INTO CONSIDERABLY BETTER AGREEMENT COMPARED  
TO RECENT DAYS WITH THE EVOLUTION OF A MAJOR NOR'EASTER THAT WILL  
BE IMPACTING AREAS OF THE MID-ATLANTIC AND NORTHEAST TONIGHT  
THROUGH EARLY SATURDAY. THE 12Z NAM AND 12Z GFS HAVE BOTH TRENDED  
STRONGER WITH THE UPPER TROUGH DIGGING ACROSS THE OHIO VALLEY THAT  
GOES NEGATIVE TILT OVER THE NORTHERN MID-ATLANTIC REGION AND  
RESULTS IN A VERY STRONG CLOSED LOW CENTER SOUTH OF LONG ISLAND  
EARLY FRIDAY. STRONG SURFACE LOW PRESSURE DEEPENING THROUGH THE  
OHIO VALLEY WILL BE REDEVELOPING JUST OFFSHORE THE MID-ATLANTIC  
AND WILL BECOME A VERY INTENSE LOW CENTER SOUTHEAST OF NEW ENGLAND  
BY LATE FRIDAY AND ALL OF THE MODELS AGREE WITH THAT, BUT THE NAM  
IS LIKELY WRAPPING ITS LOW CENTER A BIT TOO FAR TO THE NORTH AND  
WEST, AND AS A RESULT HAS A STRONG MID LEVEL DEFORMATION ZONE  
WRAPPED FARTHER BACK TO THE NORTHWEST WHICH RESULTS IN A HEAVIER  
QPF AXIS FARTHER BACK ACROSS ESPECIALLY SOUTHEAST NY. THE NAM ALSO  
APPEARS TO HAVE TOO MUCH COLD AIR IN THE BOUNDARY LAYER  
CONSIDERING THE DEGREE OF COLD AIR INITIALLY IN PLACE, ALONG WITH  
THE FACT THAT THERE WILL BE VERY STRONG ATLANTIC INFLOW WHICH WILL  
TEND TO MODERATE THE THERMAL PROFILES IN THE LOW LEVELS. OVERALL,  
THE 12Z CMC APPEARED TO PERIODICALLY BE TOO WEAK AT LEAST THROUGH  
FRIDAY WITH THE SYSTEM. THE BETTER MODEL CLUSTERING IS NOTED WITH  
THE 12Z GFS AND 12Z ECMWF WHICH ALSO HAS BETTER SUPPORT FROM THE  
12Z UKMET AND THE LATEST GEFS MEAN AND ECENS MEAN.  
 
   
..DEEP CLOSED LOW IMPACTING THE WESTERN U.S. THROUGH SATURDAY
 
   
..NEGATIVELY TILTED TROUGH APPROACHING THE PLAINS ON SUNDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS ALL TAKE A VERY STRONG CLOSED LOW SOUTH AND OFFSHORE  
THE PACIFIC NORTHWEST TODAY WHICH BROADENS OUT OVER THE NEXT  
COUPLE OF DAYS WHILE ALSO MOVING INLAND ACROSS THE INTERMOUNTAIN  
REGION. THIS WILL ALLOW A BROAD TROUGH TO ENVELOPE ALL OF THE WEST  
THROUGH SUNDAY. THE GUIDANCE THOUGH INDICATES THAT ENERGY LIFTING  
OUT OF THE BASE OF THE TROUGH BY LATE SUNDAY WILL ALLOW THE TROUGH  
TO TAKE ON A NEGATIVE TILT TOWARD THE HIGH PLAINS REGION. THERE IS  
REASONABLY GOOD AGREEMENT WITH THE GUIDANCE THROUGH ABOUT 60  
HOURS, AND THEN AFTER THAT THE 12Z NAM IS A BIT OF A FASTER  
OUTLIER IN TAKING ITS ENERGY OUT INTO THE PLAINS WHICH RESULTS IN  
A FASTER FRONTAL PROGRESSION. THE GLOBAL MODELS ARE REASONABLY  
WELL CLUSTERED AT THIS TIME, AND SO A NON-NAM CONSENSUS WILL BE  
PREFERRED.  
 
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