040  
FXUS10 KWNH 120510  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1210 AM EST SUN NOV 12 2017  
 
VALID NOV 12/0000 UTC THRU NOV 15/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH LATEST MODEL PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
INITIALIZATIONS: THE 12Z CMC APPEARS TO HAVE INITIALIZED AND NEAR  
TERM (0-12 HOUR) FORECAST HEIGHTS ALOFT THAT ARE HIGHER THAN THE  
OTHER AVAILABLE MODELS. THIS EVENTUALLY GROWS INTO LARGER  
DIFFERENCES OVER MOST OF THE EASTERN AND SOUTHERN CONUS THROUGH  
THE NEXT SEVERAL DAYS...WITH A SYSTEMATIC BIAS TOWARD HIGHER  
HEIGHTS AND A NORTHWARD POSITION OF SOME FEATURES. THUS...THE 12Z  
CMC IS EXCLUDED FROM THE PREFERENCES FOR ALL THE SYSTEMS IN THIS  
DISCUSSION.  
 
   
..LEAD SHORTWAVE PROGRESSING FROM ONTARIO THIS MORNING
 
TO THE  
CANADIAN MARTIMES BY MONDAY MORNING...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THERE ARE NO APPRECIABLE DIFFERENCES IN THE MODEL MASS FIELDS FOR  
THIS SYSTEM AND A GENERAL BLEND IS RECOMMENDED WITH HIGH  
CONFIDENCE.  
 
   
..BROAD SECONDARY TROUGH OVER THE CENTRAL PLAINS PUSHING EAST
 
 
...GRADUALLY WAVE AMPLIFICATION OVER THE EASTERN CONUS THROUGH  
MONDAY WITH SURFACE WAVE DEVELOPMENT OFF THE EAST COAST...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z GFS / 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
MODELS SHOW THE SAME GENERAL EVOLUTION -- WITH A BROAD TROUGH  
CURRENTLY OVER THE PLAINS GRADUALLY AMPLIFYING AND EVENTUALLY  
LEADING TO THE DEVELOPMENT OF A SURFACE LOW WELL OFFSHORE OF THE  
EAST COAST ONCE THE TROUGH REACHES THE ATLANTIC. THE SURFACE LOW  
DEVELOPMENT WITH THIS SYSTEM APPEARS TO BE FAR ENOUGH OFFSHORE  
THAT THERE MAY NOT BE MUCH IMPACT ON SENSIBLE WEATHER DESPITE SOME  
DIFFERENCES IN THE MODELS. THE PREFERENCE OVER THE PAST SEVERAL  
MODEL CYCLES HAS BEEN TO LEAN TOWARD THE ECMWF AND GFS WHICH SHOW  
WEAKER CYCLOGENESIS THAT IS DISPLACED A LITTLE FURTHER SOUTH. THIS  
SOLUTION HAS HAD THE MOST SUPPORT FROM GEFS AND ECMWF  
ENSEMBLES...AND THAT CONTINUES TO BE THE CASE. THE DIFFERENCE IN  
STRENGTH OF THE CYCLOGENESIS APPEARS TO BE PRIMARILY RELATED TO  
THE STRENGTH OF THE GRADUALLY AMPLIFYING WAVE...AND THE GFS AND  
ECMWF HAVE BEEN MOST CONSISTENT IN THEIR DEPICTIONS.  
THEREFORE...THE PREFERENCE IS TO CONTINUE A BLEND OF THE GFS AND  
ECMWF.  
 
   
..UPPER TROUGH/CLOSED LOW OFFSHORE OF THE PACIFIC NORTHWEST
 
 
...UPPER LEVEL LOW DEVOLVING TO A SHORTWAVE AND EJECTING EAST TO  
THE NORTHERN PLAINS BY WEDNESDAY MORNING....   
..DEEP CYCLONE REFORMING OFFSHORE BRITISH COLUMBIA BY TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 18Z GEFS MEAN / 12Z ECMWF ENS MEAN  
CONFIDENCE: AVERAGE  
 
MODELS CONTINUE TO SHOW DIFFERENCES IN HOW THE CURRENT CLOSED LOW  
OFF THE PACIFIC NORTHWEST DEVOLVES INTO AN OPEN WAVE AND KICKS  
ONSHORE. THE 00Z GFS SHOWS A NOTABLE TREND TOWARD A STRONGER  
SURFACE LOW DEVELOPING ABOUT 150-200 MILES OFFSHORE AND THEN  
TRACKING ACROSS THE NORTHWEST CORNER OF THE OLYMPIC PENINSULA.  
THIS TREND BEGAN ON THE 18Z RUN...BUT IT IS SUBSTANTIALLY DEEPER  
AND FURTHER SOUTHEAST WITH THE SURFACE LOW POSITION THAN RUNS  
PRIOR TO THAT. THE 12Z UKMET ACTUALLY SHOWS SOME SIMILARITY TO  
THIS. EXAMINING THE VORTICITY FIELDS...THE GFS SHOWS A SIGNIFICANT  
INCREASE IN POTENTIAL VORTICITY IN THE MID-LEVELS ON SUNDAY  
NIGHT...WHICH COULD BE DUE TO THE INFLUENCE OF LATENT HEAT RELEASE  
AS IT CORRESPONDS TO A MAXIMUM IN QPF AS WELL. THE RAPID INCREASE  
IN MID-UPPER LEVEL VORTICITY AS THE CLOSED LOW OPENS INTO A WAVE  
SEEMS LIKE A LOWER LIKELIHOOD SCENARIO...AND GIVEN THAT THIS IS A  
NEW TREND...THE PREFERENCE IS TO LEAN AWAY FROM IT FOR NOW.  
HOWEVER...THE TREND WILL NEED TO BE MONITORED AS IT WOULD LIKELY  
LEAD TO MORE IMPACTS IN THE PACIFIC NORTHWEST.  
 
THE 12Z ECMWF IS FURTHER NORTHWEST WITH THE SURFACE LOW AND DOES  
NOT SHOW AS RAPID A RAMP UP IN THE VORTICITY FIELDS AS THE GFS.  
THIS SEEMS MORE LIKELY. HOWEVER...AS THE GEFS ENSEMBLE MEAN AND  
ECMWF ENSEMBLE MEAN ARE SITUATED BETWEEN THE TWO...THEY DO LEND  
MORE CREDENCE TO A STRONGER AND MORE SOUTHERLY PLACEMENT OF THE  
LOW. THEREFORE...THE PREFERENCE FOR THE MASS FIELDS WITH THIS  
SYSTEM IS FOR A BLEND OF THE ENSEMBLE MEANS. THE DIFFERENCES WITH  
THE REFORMING CYCLONE FURTHER TO THE NORTH ON MONDAY NIGHT AND  
TUESDAY ARE NOT QUITE AS SIGNIFICANT AND A BLEND OF THE ENSEMBLE  
MEANS SHOULD STILL BE FAIRLY REPRESENTATIVE.  
 
   
..WEAK SHORTWAVE DEVELOPING OVER THE NORTHEAST BY LATE TUESDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 18Z GEFS MEAN / 12Z ECMWF  
CONFIDENCE: AVERAGE  
 
THE 00Z 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 UKMET IS ON THE  
OPPOSITE END OF THE SPECTRUM WITH HARDLY ANY TROUGHING DEPICTED AS  
IT KEEPS THE VORT MAX ALOFT VERY SHEARED OUT. THE MOST LIKELY  
SCENARIO APPEARS TO BE FOR A LOW-AMPLITUDE TROUGH GIVEN THE  
RELATIVELY WEAK AND ZONAL FLOW. THE 00Z NAM...12Z ECMWF...AND 18Z  
GEFS MEAN ALL INDICATE A LOW-AMPLITUDE TROUGH...WITH THE 00Z NAM A  
LITTLE FASTER THAN MOST OF THE MODELS ON TIMING. THEREFORE...THE  
PREFERENCE IS FOR A BLEND OF THE ECMWF AND GEFS MEAN AS THEY SHOW  
BETTER AGREEMENT WITH MODEL CONSENSUS TIMING.  
 
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