173  
FXUS10 KWNH 190439  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1239 AM EDT THU OCT 19 2017  
 
VALID OCT 19/0000 UTC THRU OCT 22/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION ALONG WITH MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..SHORTWAVE CLIPPING NORTHERN NEW ENGLAND BY THURS EVENING
 
   
..ASSOCIATED COLD FRONT CROSSING THE NORTHEAST BY WEEKS END
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE MASS FIELD DETAILS  
OF THIS SYSTEM. THUS A GENERAL MODEL COMPROMISE WILL BE PREFERRED.  
 
   
..ONGOING ATMOSPHERIC RIVER EVENT INTO THE WEST COAST
 
   
..LONGWAVE TROUGH EVOLUTION INTO THE WESTERN U.S. THROUGH FRI
 
   
..EJECTING OUT INTO THE PLAINS ON SAT ALONG WITH COLD FRONT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 48 HOURS  
12Z ECMWF...AFTER 48 HOURS  
CONFIDENCE: AVERAGE  
 
THE MODELS ARE IN GOOD AGREEMENT THROUGH ABOUT 48 HOURS WITH THE  
EVOLUTION OF THE LONGWAVE TROUGH AND ASSOCIATED COLD FRONT MOVING  
THROUGH THE WESTERN U.S. THEREAFTER THE MODEL ALL AGREE IN  
SHIFTING THE TROUGH OUT ACROSS THE PLAINS...BUT THERE ARE SOME  
DIFFERENCES WITH RESPECT TO THE LEVEL OF ENERGY DIGGING INTO THE  
BASE OF THE TROUGH AND ATTEMPTS FOR STREAM SEPARATION. THE 12Z CMC  
AND TO AN EXTENT THE 12Z UKMET ALLOW MORE ENERGY TO DIG TOWARD THE  
BASE OF THE TROUGH...AND AT LEAST ATTEMPT TO CLOSE OFF A MID LEVEL  
LOW CENTER IN VICINITY OF THE CENTRAL OR SOUTHERN PLAINS BY SUN.  
THE 00Z NAM/GFS AND 12Z ECMWF ALL SUGGEST MORE OF AN ELONGATED N/S  
TROUGH AXIS WITH LITTLE IN THE WAY OF SOUTHERN STREAM SEPARATION  
OR ATTEMPTS TO CLOSE OFF A NEW LOW CENTER. THE GFS DOES APPEAR TO  
BE A TAD TOO DEEP WITH ITS CLOSED LOW FEATURE BY SUN OVER SOUTHERN  
CANADA WHICH ALSO RESULTS IN A STRONGER AND MORE WRAPPED UP  
SURFACE LOW. WILL PREFER A GENERAL MODEL COMPROMISE THROUGH 48  
HOURS...FOLLOWED BY A PREFERENCE TOWARD THE ECMWF THEREAFTER.  
 
   
..SOUTHERN STREAM UPPER TROUGH REACHING THE SOUTHERN PLAINS FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
A SOUTHERN STREAM SHORTWAVE TROUGH CROSSING THE SOUTHWEST THROUGH  
THURS WILL EJECT EAST OUT ACROSS THE SOUTHERN PLAINS BY FRI OUT  
AHEAD OF THE STRONG LONGWAVE TROUGH MOVING INTO THE WESTERN U.S.  
THIS PERIOD. THE MODELS ARE IN GOOD AGREEMENT WITH THIS  
SYSTEM...SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED.  
 
   
..SHORTWAVE REACHING BRITISH COLUMBIA LATE SAT WITH WARM FRONT
 
   
..NEXT ATMOSPHERIC RIVER ARRIVING OVER THE PACIFIC NORTHWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON 12Z CMC BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS ARE IN VERY GOOD AGREEMENT IN BRINGING A STRONG WARM  
FRONT AND AN ASSOCIATED SHORTWAVE INTO THE PACIFIC NORTHWEST BY  
LATE SAT...ALONG WITH THE ARRIVAL OF THE NEXT ATMOSPHERIC RIVER  
EVENT ACROSS THE REGION. THE WARM FRONT WILL QUICKLY LIFT  
NORTHEAST ACROSS THE PACIFIC NORTHWEST BY EARLY SUN WHICH WILL BE  
FOLLOWED BY A STRONG DEEP LAYER ONSHORE FLOW PATTERN WITH ENHANCED  
RAINFALL POTENTIAL. THE 12Z CMC IS A BIT QUICKER WITH THE LEAD  
SHORTWAVE IMPULSE AND WARM FRONT BY LATE SAT...AND OVERALL IS A  
BIT OUT OF TOLERANCE COMPARED TO THE OTHERWISE WELL CLUSTERED  
GLOBAL MODELS AND INCLUDING THE NAM. WILL PREFER A NON-CMC  
CONSENSUS AS A RESULT.  
 
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ORRISON  
 

 
 
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