433  
FXUS10 KWNH 011701  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1200 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 00Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS HAVE COME INTO CONSIDERABLY BETTER AGREEMENT 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 00Z CMC APPEARED  
TO BE A LITTLE TOO WEAK WITH THE SYSTEM AS A WHOLE. THE BETTER  
MODEL CLUSTERING IS NOTED WITH THE 12Z GFS AND 00Z ECMWF WHICH  
ALSO HAS BETTER SUPPORT FROM THE 00Z 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: BLEND OF THE 12Z GFS AND 00Z ECMWF  
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 BETTER MODEL CLUSTERING RESIDES  
WITH THE 12Z GFS AND 00Z ECMWF, AND A BLEND OF THESE SOLUTIONS  
WILL BE PREFERRED.  
 
PREVIOUS MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
PREVIOUS 500 MB FORECASTS AT  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
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