196  
FXUS10 KWNH 021831  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
230 PM EDT THU NOV 02 2017  
 
VALID NOV 02/1200 UTC THRU NOV 06/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
   
..UPPER TROUGH IN THE PACIFIC NORTHWEST TODAY
 
DEAMPLIFYING AND  
EJECTING INTO THE NRN PLAINS THIS WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF / 12Z GFS / 12Z CMC  
GREATER WEIGHT TO THE 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM AND 12Z UKMET HAVE THE WAVE EJECTING THE FASTEST INTO  
CANADA...BUT ARE ALSO STRONGEST WITH THE ACCOMPANYING MID-LEVEL  
VORT MAX AND THUS SHOW STRONGER CYCLOGENESIS ACROSS SOUTHERN  
CANADA THIS WEEKEND. THIS SOLUTION DOES NOT HAVE MUCH SUPPORT FROM  
THE 00Z GEFS AND ECMWF ENSEMBLE CLUSTERS. THE REMAINDER OF THE  
MODELS SHOW SOME DIFFERENCES...BUT HAVE TRENDED MUCH CLOSER WITH  
THE 12Z CYCLE AS COMPARED TO THE 00Z CYCLE. THEREFORE...A BLEND OF  
THE ECMWF...GFS...AND CMC IS PREFERRED. THE GREATEST WEIGHT WILL  
BE PLACED ON THE ECMWF...WHICH IS ROUGHLY IN THE MIDDLE OF MODEL  
SPREAD IN TERMS OF TROUGH AMPLITUDE AND STRENGTH OF THE SURFACE  
LOW.  
 
CHANGE FROM PRELIMINARY PREFERENCE: NONE.  
 
...MID-UPPER LEVEL SHORTWAVE AMPLIFYING TOWARD THE PACIFIC  
NORTHWEST SATURDAY INTO SUNDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
MODEL AGREEMENT WITH THE MASS FIELDS FOR THIS SYSTEM IS FAIRLY  
GOOD. THE MAIN DIFFERENCE IS WITH THE 12Z NAM WHICH IS  
SUBSTANTIALLY COOLER WITH THE TEMPERATURE PROFILES OVER THE  
NORTHWEST...PARTICULARLY CLOSE TO THE COLD FRONT POSITION. GIVEN  
THIS...A NON-NAM BLEND IS PREFERRED AS THE OTHER MODELS ARE IN  
GOOD AGREEMENT.  
 
CHANGE FROM PRELIMINARY PREFERENCE: NONE.  
 
   
..UPPER LEVEL SHORTWAVE OVER THE SOUTHWEST TODAY
 
TRACKING  
EASTWARD THROUGH FRIDAY AND AMPLIFYING OVER FLORIDA ON SATURDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF / 12Z GFS / 12Z CMC  
CONFIDENCE: AVERAGE  
 
A SHORTWAVE EMBEDDED IN FAIRLY ZONAL FLOW WILL PROGRESS ACROSS THE  
SOUTHERN TIER OF STATES OVER THE NEXT DAY OR TWO BEFORE AMPLIFYING  
INTO A WEAK TROUGH ON SATURDAY IN THE VICINITY OF FLORIDA. THERE  
CONTINUES TO BE MODEL DISAGREEMENT RELATED TO THE TROUGH  
AMPLIFICATION THIS WEEKEND. THE 12Z NAM AND 12Z UKMET SHOW A  
STRONGER WAVE ALOFT AND EVENTUALLY DEVELOP A CLOSED LOW OVER SOUTH  
FLORIDA BY SUNDAY MORNING. THIS SOLUTION HAS VERY LITTLE SUPPORT  
FROM THE GEFS AND ECMWF ENSEMBLE CLUSTERS...ROUGHLY 10 PERCENT OF  
ENSEMBLE MEMBERS AND ONLY 1 CLUSTER RESEMBLED THIS SOLUTION. THE  
OTHER MODELS SHOWED A FLATTER WAVE OVERALL...AND DID TREND A  
LITTLE CLOSER TOGETHER ON THE 12Z CYCLE. THEREFORE...A BLEND OF  
THE GFS...CMC...AND ECMWF IS PREFERRED.  
 
CHANGE FROM PRELIMINARY PREFERENCE: ADD THE CMC. THE CANADIAN  
MODEL HAS TRENDED CLOSER TO THE GFS AND ECMWF...
AND IS NOW  
INCLUDED IN THE PREFERENCE.  
 
...SHORTWAVE CLIPPING THE NRN GREAT LAKES AND TRACKING ACROSS  
QUEBEC THROUGH FRIDAY WITH ASSOCIATED SURFACE LOW AND TRAILING  
COLD FRONT TO THE SOUTHWEST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
MODEL AGREEMENT FOR THIS SYSTEM IS FAIRLY HIGH AND A GENERAL MODEL  
BLEND IS PREFERRED.  
 
CHANGE FROM PRELIMINARY PREFERENCE: NONE.  
 
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