034  
FXUS10 KWNH 111845  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
145 PM 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 12Z ECMWF  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS HAVE COME INTO BETTER AGREEMENT WITH THIS SYSTEM AS THE  
12Z CMC IS NOT QUITE AS WEAK/SHEARED WITH THIS SYSTEM AS ITS  
PREVIOUS COUPLE OF RUNS. THE 12Z NAM DOES APPEAR TO BE A TAD TOO  
SLOW AND DEEP WITH ITS ENERGY COMPARED TO THE REMAINING GUIDANCE.  
OVERALL...THE BETTER MODEL CONTINUITY AND CLUSTERING STILL RESIDES  
WITH THE 12Z GFS AND 12Z ECMWF WHICH HAVE GOOD ENSEMBLE SUPPORT  
AND SUPPORT FROM THE 12Z UKMET AS WELL. WILL PREFER A BLEND OF THE  
GFS AND ECMWF.  
 
   
..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 12Z 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 12Z CMC BECOME STRONGER/MORE AMPLIFIED  
THAN THE 12Z GFS AND 12Z ECMWF. THE 12Z UKMET DID TREND JUST A  
LITTLE STRONGER THOUGH AND SOMEWHAT CLOSER TO THE NAM/CMC CAMP.  
THE CMC OVERALL IS THE MOST PROGRESSIVE SOLUTION THOUGH. 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 WELL  
CLUSTERED 12Z GFS AND 12Z ECMWF...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 12Z 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 12Z CMC GRADUALLY  
BECOMES A TAD SLOWER THAN THE MULTI-MODEL CONSENSUS...WITH THE 12Z  
UKMET PERHAPS JUST A LITTLE FASTER. THE 12Z NAM/12Z GFS AND 12Z  
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. 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 12Z UKMET DOES APPEAR TO BE A BIT TOO WEAK AT  
LEAST WITH THE NORTHERN PORTION OF THE TROUGH OVER THE NORTHEAST  
AND PERHAPS A BIT TOO STRONG WITH THE SOUTHERN PORTION DOWN OVER  
THE SOUTHEAST. THE REMAINING GUIDANCE IS CLUSTERED TOGETHER WELL  
ENOUGH THAT A NON-UKMET CONSENSUS CAN BE PREFERRED.  
 
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ORRISON  
 

 
 
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