901  
FXUS10 KWNH 140446  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1145 PM EST MON NOV 13 2017  
 
VALID NOV 14/0000 UTC THRU NOV 17/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION  
~~~~~~~~~~~~~~~~~~~~  
 
...DEVOLVING UPPER LEVEL LOW MOVING INTO SOUTHERN CANADA TODAY  
...RESULTING SHORTWAVE TROUGH PROGRESSING TOWARDS GREAT  
LAKES/NORTHEAST WEDNESDAY AND THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z ECMWF/CMC...00Z GFS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THERE WAS GENERALLY GOOD AGREEMENT IN HOW THE MODELS HANDLE THE  
ENERGY MOVING INTO CANADA TODAY. THEN DIFFERENCES BEGIN TO APPEAR  
AS THE UPPER TROUGH NEARS THE N-CNTRL 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  
COMPARED WITH PREVIOUS RUNS. THE 14/00Z GFS DID SOMETHING SIMILAR  
BUT WAS FASTER THAN THE NAM. THE 13/12Z UKMET REMAINS FARTHEST  
SOUTH OF THE DETERMINISTIC MODELS WITH THE BASE OF THE MEAN UPPER  
TROUGH AXIS WHICH IS STILL ON THE DEEPER SIDE. THE 13/12Z ECMWF  
REMAINED A REASONABLE SOLN IN THE CURRENT ENVELOPE OF  
SOLNS...ALONG WITH THE 13/12Z CMC. CYCLE.  
 
WITH THIS BEING THE CASE...THE ENSEMBLE MEANS SUPPORT A 14/00Z  
NAM/GFS AND 13/12Z ECMWF BLEND WITH THE PRIMARY SURFACE LOW  
TRACKING ACROSS SRN CANADA THROUGH THU...WITH LESS WEIGHT GIVEN TO  
THE NAM ON DAY 3 OVER THE NORTHEASTERN STATES.  
 
...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 CONTINUE TO STAND 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. THE 14/00Z RUNS OF THE NAM AND GFS REMAINED ON  
THE SLOWER BUT MUCH MORE AMPLIFIED SIDE OF THE GUIDANCE WITH THIS  
LEADING TROUGH AXIS THAN THE NON-NCEP MODELS. AT THIS  
POINT...STILL THINK A BLEND OF THE 14/00Z GFS/NAM AND 13/12Z UKMET  
SHOULD WORK WELL WITH THE LEADING EDGE OF THE TROUGH AXIS MOVING  
INLAND...AGREEING WELL WITH THE BETTER CLUSTERING OF ENSEMBLE  
MEMBERS. THE 12Z UKMET TRENDED DEEPER BUT REMAINED A LITTLE SLOWER  
THAN OTHER GLOBAL MODELS WITH THE 13/12Z CMC STILL ON THE  
FASTER/LESS LIKELY SIDE OF THE GUIDANCE.  
 
...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 GEFS HAS BEEN  
CONSISTENTLY FASTER BY 00Z/17. THE 14/00Z RUN OF THE GFS SLOWED  
COMPARED WITH THE PREVIOUS RUNS AND WAS IN SOMEWHAT BETTER  
AGREEMENT WITH THE PREVIOUS ECMWF. 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.  
 
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WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
BANN  
 

 
 
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