115  
FXUS10 KWNH 111657  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1156 AM EST SAT NOV 11 2017  
 
VALID NOV 11/1200 UTC THRU NOV 15/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
   
..LEAD SHORTWAVE OVER NORTHERN MN
 
EJECTING EAST ALONG THE  
US-CANADA BORDER THROUGH THE WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE LATEST CONCERN WITH THE GUIDANCE INVOLVING THIS SYSTEM ASIDE  
FROM THE FACT THAT THE 00Z CMC AGAIN APPEARS TOO SHEARED/WEAK WITH  
IT...IS THAT THE 12Z NAM AND 00Z UKMET MAY BECOME A LITTLE TOO  
SLOW BY LATER SUNDAY AS IT PASSES ACROSS SOUTHERN QUEBEC AND NEAR  
NORTHERN MAINE. THE 12Z GFS AND 00Z ECMWF ARE CLUSTERED A LITTLE  
FASTER AND HAVE GOOD ENSEMBLE SUPPORT. WILL FAVOR A GFS/ECMWF  
BLEND AT THIS TIME.  
 
   
..SECONDARY TROUGH OVER THE INTERMOUNTAIN WEST PROGRESSING EAST
 
 
...GRADUALLY AMPLIFYING WAVE OVER THE EASTERN CONUS FROM SUNDAY  
INTO MONDAY WITH SURFACE WAVE DEVELOPMENT OFF THE EAST COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z GFS AND 00Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM CROSSES THE  
PLAINS AND MUCH OF THE OH VALLEY THROUGH SUNDAY AND SUNDAY NIGHT.  
HOWEVER...AS THE ENERGY APPROACHES THE MID-ATLANTIC AND NEW  
ENGLAND...THE 12Z NAM AND ESPECIALLY THE 00Z CMC BECOME  
STRONGER/MORE AMPLIFIED THAN THE 12Z GFS/00Z UKMET AND 00Z ECMWF.  
THE UKMET ACTUALLY BECOMES THE WEAKEST AND MOST PROGRESSIVE AS THE  
ENERGY REACHES THE COAST. ALL OF THE MODELS AGREE THAT SURFACE  
CYCLOGENESIS WILL TAKE PLACE WELL EAST OF NEW ENGLAND...BUT THE  
STRONGER NAM AND CMC SHORTWAVE AMPLIFICATION RESULT IN A LOW  
CENTER DEEPER THAN THE MODEL CONSENSUS. THE EXPECTATION IS FOR A  
RELATIVELY WEAKER LOW THAT IS PROGRESSIVE WHICH WILL TEND TO LIMIT  
THE IMPACTS TO NEW ENGLAND. OVERALL...THERE IS STRONGER ENSEMBLE  
SUPPORT WITH THE GFS AND ECMWF SOLUTIONS...AND SO A BLEND OF THESE  
WILL BE PREFERRED.  
 
...DEEP UPPER TROUGH/CLOSED LOW DROPPING SOUTH OFFSHORE THE  
PACIFIC NORTHWEST...  
...ENERGY ADVANCING INLAND ACROSS THE NORTHWEST AND DOWNSTREAM TO  
THE NORTHERN PLAINS BY TUESDAY....  
...DEEP LAYER CYCLONE REFORMING OFFSHORE BRITISH COLUMBIA BY  
TUESDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z NAM/12Z GFS AND 00Z ECMWF  
CONFIDENCE: ABOVE AVERAGE  
 
THE GUIDANCE CONTINUES TO ALLOW A DEEP UPPER TROUGH AND ASSOCIATED  
CLOSED LOW TO DROP SOUTH THROUGH SUNDAY 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. THE 00Z CMC GRADUALLY  
BECOMES A TAD SLOWER THAN THE MULTI-MODEL CONSENSUS...WITH THE 00Z  
UKMET PERHAPS JUST A LITTLE FASTER. THE 12Z NAM/12Z GFS AND 00Z  
ECMWF ARE ALL CLUSTERED IN BETWEEN.  
 
MEANWHILE...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 MODEL SPREAD IS FAIRLY  
MINIMAL WITH THE EVOLUTION OF THIS NEXT SYSTEM...ALTHOUGH THE  
UKMET MAY BE TAD TOO WEAK WITH ITS HEIGHT FALLS OFFSHORE THE  
NORTHWEST BY TUESDAY. GENERALLY...THE NAM/GFS AND ECMWF CLUSTER  
THE BEST AND MORE CLOSELY APPROXIMATE THE MODEL CONSENSUS...AND  
THUS A BLEND OF THESE SOLUTIONS WILL BE PREFERRED ACROSS THE  
NORTHWEST WITH THESE SYSTEMS.  
 
   
..WEAK SHORTWAVE OVER THE EASTERN SEABOARD BY LATE TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-UKMET CONSENSUS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS SHOW A WEAK AND BROAD DEGREE OF TROUGHING ALONG THE  
EASTERN SEABOARD BY THE END OF THE PERIOD. MODEL SPREAD IS FAIRLY  
MODEST...BUT THE 00Z UKMET DOES APPEAR TO BE A BIT TOO WEAK. THE  
REMAINING GUIDANCE IS FAIRLY WELL CLUSTERED AND WITHIN THE  
ENSEMBLE SPREAD...SO WILL PREFER A NON-UKMET CONSENSUS AT THIS  
POINT.  
 
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