082  
FXUS10 KWNH 140708  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
208 AM EST TUE NOV 14 2017  
 
VALID NOV 14/0000 UTC THRU NOV 17/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
FINAL 00Z MODEL EVALUATION AND PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...DEVOLVING UPPER LEVEL LOW MOVING INTO SOUTHERN CANADA TODAY  
...RESULTING SHORTWAVE TROUGH PROGRESSING TOWARDS GREAT  
LAKES/NORTHEAST WEDNESDAY AND THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 14/00Z ECMWF/CMC/GFS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THERE WAS GENERALLY GOOD AGREEMENT IN HOW THE MODELS HANDLE THE  
ENERGY MOVING INTO CANADA TODAY. THEN DIFFERENCES APPEAR AS THE  
UPPER TROUGH NEARS THE NORTH CENTRAL PORTION OF THE U.S. BY WED  
MORNING...ESPECIALLY WITH RESPECT TO SOME TIMING DIFFERENCES OF  
TWO SMALLER WAVELENGTH SHORTWAVES WITHIN THE BROADER TROUGH AXIS.  
 
THE 14/00Z NAM KEPT REASONABLY GOOD CONTINUITY WITH THE NORTHERN  
VORT OVER CANADA BUT SLOWED AND STRENGTHENED THE SOUTHERN VORT  
UPON CROSSING THE INTERNATIONAL BORDER COMPARED WITH PREVIOUS  
RUNS. THE 14/00Z GFS DID SOMETHING SIMILAR BUT WAS FASTER THAN  
THE NAM OR THE 14/00Z ECMWF. THE 14/00Z UKMET REMAINED ON THE  
DEEPER SIDE OF THE MODEL GUIDANCE BUT THE WAS NOT QUITE AS MUCH OF  
AN OUTLIER AS IT WAS ON MONDAY. THE 14/00 ECMWF REMAINED A  
REASONABLE SOLN.  
 
...LEADING SHORTWAVE OF LONGWAVE TROUGH AXIS ALONG THE WEST COAST  
WED INTO THU...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~~~~~~~~~~~~  
PREFERENCE: 14/00Z GFS AND 13/12Z UKMET  
CONFIDENCE: AVERAGE  
 
THE 13/00Z AND 13/12Z ECWMF RUNS STOOD OUT WITH THE LEADING EDGE  
OF THE TROUGH AXIS AS A NEAR OUTLIER WITH SHORTWAVE RIDGING BEHIND  
THE LEADING SHORTWAVE INTO SRN ALBERTA/SASKATCHEWAN THU MORNING  
AND THE REMAINING LARGER TROUGH AXIS JUST OFFSHORE OF THE WEST  
COAST. THERE WAS A SUBTLE SHIFT BY THE ECMWF TOWARDS THE GFS/NAM  
IDEA. AT THIS POINT...STILL THINK A BLEND OF THE 14/00Z  
GFS/NAM/UKMET SHOULD WORK WELL WITH THE LEADING EDGE OF THE TROUGH  
AXIS MOVING INLAND...AGREEING WELL WITH THE BETTER CLUSTERING OF  
ENSEMBLE MEMBERS.  
 
...TRAILING LONGWAVE TROUGH AXIS PROGRESSING ACROSS THE WEST COAST  
ON THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~~~~~~~~~~~~  
PREFERENCE: 14/00Z NAM/UKMET AND 13/00Z ECMWF  
CONFIDENCE: BELOW AVERAGE  
 
THE ECMWF ENSEMBLE MEAN HAS BEEN CONSISTENT WITH A SLOWER TROUGH  
AXIS PROGRESSING ACROSS THE WEST COAST WHILE THE GFS/GEFS HAS BEEN  
CONSISTENTLY FASTER BY 17/00Z. THE 14/00Z RUN OF THE GFS DID SLOW  
COMPARED WITH THE PREVIOUS RUNS AND WAS IN SOMEWHAT BETTER  
AGREEMENT WITH THE ECMWF. THE 14/00Z ECMWF DID A GOOD JOB IN  
MAINTAINING CONTINUITY FROM PREVIOUS RUNS...ALTHOUGH ITS TROUGH  
AXIS WAS SLIGHTLY NORTH OF THE PREVIOUS RUNS. GIVEN THE GFS HAS A  
KNOWN BIAS FOR PROGRESSING THESE TYPES OF SYSTEMS TOO QUICKLY  
TOWARD THE EAST AND THE ABUNDANCE OF ENSEMBLE GUIDANCE THAT IS  
SLOWER THAN THE GFS/GEFS...THE PREFERENCE IS STILL TO BE SOMEWHERE  
IN THE MIDDLE. CONFIDENCE REMAINS BELOW AVERAGE GIVEN THE MODEL  
SPREAD.  
 
   
..SHORTWAVE AMPLIFYING OVER THE NORTHEAST BY LATE TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
BANN  
 

 
 
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