349  
FXUS10 KWNH 011845  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
144 PM EST THU FEB 01 2018  
 
VALID FEB 01/1200 UTC THRU FEB 05/0000 UTC  
 
 
VALID FEB 1/1200 UTC THROUGH FEB 05/0000 UTC  
   
.SEE NOUS42 KWNO (ADMNFD) FOR UPPER AIR INGEST STATUS
 
 
   
..12Z MODEL EVALUATION WITH FINAL PREFERENCES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
 
 
...COLD FRONT MOVING ACROSS THE GREAT LAKES THROUGH THE MS VALLEY  
TONIGHT  
INTO FRI...  
...SURFACE LOW PRESSURE FORMING ON THE FRONT OVER SOUTHWEST QUEBEC  
INTO  
NORTHERN NEW ENGLAND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 12Z GFS/12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM WAS CLOSE TO THE MODEL CONSENSUS WITH A SHORT WAVE  
TRACKING FROM THE UPPER GREAT LAKES INTO NORTHERN NEW ENGLAND  
TONIGHT INTO FRI, BUT SPEEDS UP ACROSS NORTHERN NEW ENGLAND DURING  
FRI/FRI NIGHT. SURFACE LOW PRESSURE FORMING ON THE FRONT AHEAD OF  
THE SHORT WAVE DEEPENS MUCH MORE QUICKLY ACROSS NORTHERN NEW  
ENGLAND FRI INTO FRI NIGHT, WHICH IS A MODEL BIAS FOR THE NAM.  
 
THE 12Z GFS WAS CLOSER TO THE CONSENSUS WITH THE SHORT WAVE AND  
SURFACE LOW AS THEY CROSS NORTHERN NEW ENGLAND FRI NIGHT FRI  
NIGHT. ITS SOLUTION IS CLOSE TO THE 12Z ECMWF, AS WELL AS THE  
ENSEMBLE MEANS OF EACH OF THESE SOLUTIONS. BECAUSE OF THIS, A  
BLEND OF THE 12Z GFS/12Z ECMWF WAS THE PREFERRED SOLUTION.  
 
 
...SHORT WAVE CROSSING THE PACIFIC NORTHWEST FRI INTO FRI NIGHT,  
BEFORE TRACKING INTO THE ROCKIES DURING SAT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 12Z GFS/12Z ECMWF/12Z UKMET BLEND  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM IS INITIALLY CLOSE TO THE CONSENSUS AS THE SHORT WAVE  
CROSSES WA AND NORTHERN ROCKIES DURING FRI INTO FRI NIGHT. AFTER  
THAT TIME, THE 12Z NAM BECOMES FASTER AND DEEPER WITH THE SHORT  
WAVE AS IT CROSSES THE CENTRAL AND SOUTHERN ROCKIES. BY CONTRAST,  
THE 12Z GFS SOLUTION IS CLOSER TO THE 12Z ECWMF/UKMET THROUGHOUT  
THE LIFE CYCLE OF THE SHORT WAVE...WHICH REACHES THE SOUTHERN  
PLAINS BY 00Z SUN. THESE SOLUTIONS ARE SUPPORTED BY THE ENSEMBLE  
MEAN SOLUTIONS AS WELL.  
 
 
...SHORT WAVE TRACKING FROM WESTERN CANADA INTO THE NORTHERN  
PLAINS,  
REACHING THE UPPER GREAT LAKES SUN...  
...SURFACE LOW PRESSURE FORMING ON A FRONTAL BOUNDARY OVER WESTERN  
NEW ENGLAND SUN INTO SUN NIGHT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: 12Z GFS/12Z ECMWF BLEND  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE 12Z NAM IS CLOSE TO THE CONSENSUS AS THE SHORT WAVE TRACKS OUT  
OF WESTERN CANADA INTO THE NORTHERN PLAINS FRI INTO SAT, BUT IT  
BECOMES FASTER AND DEEPER WITH THE SHORT WAVE AS IT CROSSES THE  
UPPER GREAT LAKES BY 05/00Z. BECAUSE OF THIS, ITS DEVELOPING  
SURFACE LOW BECOMES DEEPER AND FASTER AS IT CROSSES INTO SOUTHWEST  
QUEBEC SUN EVENING.  
 
THE 12Z GFS REMAINS CLOSER TO THE CONSENSUS THROUGH 12Z SUN, THEN  
BECOMES SLOWER THAN THE CONSENSUS THROUGH 00Z MON WITH ITS MID  
LEVEL SHORT WAVE AND SURFACE LOW (THE SLOWING IS SUPPORTED BY THE  
00Z GEFS MEAN). THE 12Z ECMWF IS SOMEWHERE IN THE MIDDLE OF THE  
12Z NAM/GFS SOLUTIONS, AND IS SUPPORTED BY THE 00Z ECWMF MEAN. THE  
WPC PREFERENCE IS FOR A 12Z GFS/12Z ECWMF BLEND, IN AN ATTEMPT TO  
MITIGATE SOME OF THE TIMING DIFFERENCES. HOWEVER, BECAUSE OF THE  
MODEL SPREAD, FORECAST CONFIDENCE REMAINS BELOW AVERAGE.  
 
 
...SHORT WAVE ENERGY TRACKING FROM THE SOUTHERN PLAINS ACROSS THE  
SOUTHEAST SAT INTO SUN...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THERE WAS GOOD MODEL CONSENSUS WITH THE SHORT WAVE TRACKING OUT OF  
THE SOUTHERN PLAINS SAT INTO THE SOUTHEAST DURING SUN, AND THERE  
IS SIMILARITY WITH RESPECT TO THE PLACEMENT OF THE AXES OF MAXIMUM  
QPF ACROSS THE SOUTHEAST SAT NIGHT INTO SUN.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
HAYES  
 
 

 
 
 

 
 
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