779  
FXUS10 KWNH 121706  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1206 PM EST SUN NOV 12 2017  
 
VALID NOV 12/1200 UTC THRU NOV 16/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..LEAD SHORTWAVE CROSSING SOUTHERN QUEBEC/NORTHERN MAINE
 
   
..REACHING THE CANADIAN MARTIMES BY MONDAY MORNING
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THERE ARE NO APPRECIABLE DIFFERENCES IN THE MODEL MASS FIELDS FOR  
THIS SYSTEM AND THUS A GENERAL MODEL BLEND WILL BE PREFERRED.  
 
   
..BROAD SECONDARY TROUGH OVER THE MIDWEST PUSHING EAST
 
 
...AMPLIFICATION OVER THE EASTERN CONUS THROUGH MONDAY WITH  
SURFACE WAVE DEVELOPMENT OFF THE EAST COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z CMC  
CONFIDENCE: AVERAGE  
 
THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM THROUGH TONIGHT  
AS IT CROSSES THE MIDWEST AND OH VALLEY. AS THE ENERGY REACHES THE  
MID-ATLANTIC AND NORTHEAST ON MONDAY IT WILL BEGIN TO AMPLIFY  
SOMEWHAT AND SHOULD FOSTER A WAVE OF LOW PRESSURE EAST OF NEW  
ENGLAND LATER MONDAY NIGHT BEFORE THEN LIFTING NORTHEAST AND OUT  
TO SEA ON TUESDAY. THE 12Z NAM OVERALL IS THE DEEPEST SOLUTION  
WITH RESPECT TO THE LEVEL OF TROUGH AMPLIFICATION...HOWEVER THE  
12Z GFS WHICH HAD BEEN WEAKER HAS TRENDED A BIT STRONGER AND IS  
ONLY A TAD WEAKER THAN THE NAM. THE 00Z UKMET AND 00Z ECMWF ARE  
THE WEAKEST WITH THE UKMET OVERALL THE MOST PROGRESSIVE AS THE  
ENERGY PUSHES OFFSHORE. THE 00Z CMC IS GENERALLY IN BETWEEN THE  
GFS AND ECMWF SOLUTIONS. THERE IS A BIT OF GROWING SPREAD  
CURRENTLY WITH THE DEGREE OF AMPLIFICATION OF THIS SYSTEM. A BLEND  
OF THE GFS AND CMC WOULD BEST APPROXIMATE THE MODEL CONSENSUS AT  
THIS POINT...AND SO A BLEND OF THESE SOLUTIONS WILL BE PREFERRED  
WHICH WILL COMPROMISE BETWEEN THE STRONGER NAM AND THE WEAKER  
ECMWF/UKMET CAMP.  
 
   
..UPPER TROUGH/CLOSED LOW OFFSHORE OF THE PACIFIC NORTHWEST
 
 
...UPPER LEVEL LOW DEVOLVING TO A SHORTWAVE AND EJECTING EAST TO  
THE NORTHERN PLAINS/MIDWEST BY WEDNESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS/00Z UKMET AND 00Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE GUIDANCE ALLOWS A DEEP UPPER TROUGH AND ASSOCIATED CLOSED LOW  
TO DROP SOUTH THROUGH TODAY OFFSHORE THE PACIFIC NORTHWEST BEFORE  
THEN PIVOTING EAST AND INLAND ACROSS THE NORTHWEST THROUGH MONDAY.  
THIS WILL DRIVE LOW PRESSURE ACROSS VANCOUVER ISLAND AND A COLD  
FRONT INLAND ACROSS THE COASTAL RANGES OF WA/OR AND INTERIOR  
SECTIONS OF THE NORTHWEST. BY TUESDAY...THIS ENERGY WILL BE  
RAPIDLY MOVING DOWNSTREAM ACROSS THE NORTHERN PLAINS AS A  
PROGRESSIVE SHORTWAVE TROUGH. ON WEDNESDAY THE ENERGY WILL BE  
TENDING TO AMPLIFY A BIT ACROSS THE UPPER MIDWEST AND GREAT LAKES  
REGION. THE 12Z NAM APPEARS TO BE A LITTLE SLOW AND PERHAPS A TAD  
TOO FAR SOUTH WITH THE ARRIVAL SURFACE LOW PRESSURE NEAR THE  
OLYMPIC PENINSULA AND THE SOUTHERN TIP OF VANCOUVER ISLAND. THE  
00Z CMC FOR ITS PARTS ALSO IS PROBABLY TOO SLOW BUT APPEARS TOO  
FAR NORTH. THE 12Z GFS AND 00Z UKMET AND 00Z ECMWF ARE CLUSTERED  
TOGETHER IN BETWEEN THE NAM AND CMC BUT ARE A TAD MORE  
PROGRESSIVE. DOWNWIND AS THE ENERGY OPENS UP INTO A PROGRESSIVE  
TROUGH ALOFT CROSSING THE NORTHERN PLAINS AND MIDWEST...THE 00Z  
CMC BECOMES A WEAK OUTLIER...AND THE 12Z NAM ALSO APPEARS TOO WEAK  
AND TOO FAR NORTH WITH ITS SURFACE LOW EVOLUTION. BETTER MODEL  
CLUSTERING AND ENSEMBLE SUPPORT RESIDES WITH THE GFS/UKMET AND  
ECMWF...AND THUS A BLEND OF THESE SOLUTIONS WILL BE PREFERRED.  
 
   
..DEEP CYCLONE REFORMING OFFSHORE BRITISH COLUMBIA BY TUESDAY
 
   
..ENERGY IMPACTING THE PACIFIC NORTHWEST BY WEDNESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS/00Z CMC AND 00Z ECMWF  
CONFIDENCE: AVERAGE  
 
A NEW DEEP CLOSED LOW WILL BE FORMING AND DROPPING SOUTH OFFSHORE  
BRITISH COLUMBIA BY TUESDAY...AND SETTING THE STAGE FOR DEEP LAYER  
CYCLONIC AND ONSHORE FLOW TO IMPACT THE COASTAL RANGES OF THE  
PACIFIC NORTHWEST. THE 12Z NAM IS THE SLOWEST IN BRINGING THE  
HEIGHT FALLS/ENERGY TOWARD THE PACIFIC NORTHWEST BY WEDNESDAY AND  
IS ALSO PROBABLY BIT TOO WEAK WITH ITS SURFACE LOW. THE 00Z UKMET  
HOWEVER IS A BIT OF A DEEPER OUTLIER WITH ITS CLOSED LOW BY THE  
END OF THE PERIOD WHICH ALSO RESULTS IN A STRONGER SURFACE LOW.  
THE 12Z GFS/00Z CMC AND 00Z ECMWF TEND TO CLUSTER TOGETHER A BIT  
BETTER IN BETWEEN THE NAM AND UKMET SOLUTIONS...BUT ALSO TEND TO  
BRING THEIR HEIGHT FALLS INLAND TOWARD THE PACIFIC NORTHWEST A TAD  
QUICKER. A BLEND OF THESE SOLUTIONS WILL BE PREFERRED.  
 
   
..WEAK SHORTWAVE DEVELOPING OVER THE NORTHEAST BY LATE TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECENS MEAN  
CONFIDENCE: SLIGHTLY BELOW AVERAGE  
 
THE 12Z GFS SHOWS A MUCH STRONGER AND MORE AMPLIFIED TROUGH THAN  
THE OTHER MODELS FOR THIS SYSTEM...WITH A CLOSED LOW DEVELOPING  
ALOFT OVER THE NORTHEAST BY TUESDAY NIGHT. THE 12Z NAM IS ALSO  
RATHER STRONG AS WELL BUT NOT QUITE TO THE EXTENT OF THE GFS. THE  
00Z CMC AND 00Z UKMET ARE THE WEAKEST SOLUTIONS...WITH THE 00Z  
ECMWF IN BETWEEN WEAKER AND STRONGER CAMPS. HOWEVER...THE ECMWF  
MAY BE A TAD TOO SLOW. THE MOST LIKELY SCENARIO APPEARS TO BE FOR  
A LOW-AMPLITUDE TROUGH GIVEN THE RELATIVELY WEAK AND ZONAL FLOW.  
THE 06Z GEFS MEAN TENDS TO SUPPORT THE STRONGER OPERATIONAL  
GFS...BUT THE 00Z ECENS MEAN MOST CLOSELY FITS THE MODEL CONSENSUS  
IN BETWEEN THE STRONGER AND WEAKER SOLUTIONS. WILL FAVOR THE ECENS  
MEAN AT THIS TIME AS A RESULT.  
 
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