208  
FXUS10 KWNH 021647  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1247 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 PRELIMINARY PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
   
..UPPER TROUGH IN THE PACIFIC NORTHWEST TODAY
 
DEAMPLIFYING AND  
EJECTING INTO THE NRN PLAINS THIS WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z ECMWF / 12Z GFS / 00Z CMC  
GREATER WEIGHT TO THE 00Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE 12Z NAM AND 00Z 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 GEFS AND ECMWF ENSEMBLE CLUSTERS...AND IN GENERAL WOULD NOT  
EXPECT THE STRONGEST VERSION OF AN EJECTING WAVE TO BE THE FASTEST  
SOLUTION. THE REMAINDER OF THE MODELS DO SHOW SOME  
DIFFERENCES...BUT CONFIDENCE IS NOT HIGH ENOUGH IN ANY PARTICULAR  
SOLUTION TO ELIMINATE THE OTHERS. 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 ASSOCIATED  
VORT MAX...BUT IS SLOWER THAN THE NAM AND UKMET WHICH SEEMS MORE  
LIKELY.  
 
...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.  
 
   
..UPPER LEVEL SHORTWAVE OVER THE SOUTHWEST TODAY
 
TRACKING  
EASTWARD THROUGH FRIDAY AND AMPLIFYING OVER FLORIDA ON SATURDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z ECMWF / 12Z GFS  
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 00Z CMC 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  
OTHERS GENERALLY SHOWED A FLATTER WAVE ON THE 5820M ISOHEIGHT AT  
500MB. THE 00Z UKMET WAS MUCH FLATTER WITH THE WAVE THAN OTHER  
MODELS...DESPITE A STRONGER MID-LEVEL VORT MAX THAN THE ECMWF AND  
GFS. THIS ALSO SEEMS LIKE A LESS LIKELY SOLUTION. THEREFORE...THE  
PREFERENCE IS TOWARD A BLEND OF THE 00Z ECMWF AND 12Z GFS.  
 
...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.  
 
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