650  
FXUS10 KWNH 121859  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
159 PM EST TUE DEC 12 2017  
 
VALID DEC 12/1200 UTC THRU DEC 16/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH LATEST PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..DEEPENING/NEGATIVELY TILTED CYCLONE IMPACTING THE NORTHEAST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS OVER THE NEXT 36 HOURS SHOW GOOD MASS FIELD AGREEMENT  
WITH THE DETAILS OF THE STRENGTHENING AND NEGATIVELY TILTING  
TROUGH OVER THE NORTHEAST. LOW PRESSURE INITIALLY OVER WESTERN NY  
WILL RECONSOLIDATE OVER SOUTHERN NEW ENGLAND LATER THIS AFTERNOON  
AND THEN LIFT NORTH UP ACROSS CENTRAL AND DOWNEAST MAINE BY EARLY  
WEDNESDAY. THE SYSTEM WILL EXIT UP ACROSS QUEBEC ON THURSDAY. WILL  
PREFER A GENERAL MODEL BLEND AT THIS TIME.  
 
   
..STRONG SHORTWAVE ENTERING BRITISH COLUMBIA TODAY
 
   
..ENERGY AND ASSOCIATED CLIPPER LOW DIGGING SOUTHEAST
 
   
..CROSSING THE UPPER MIDWEST/OH VALLEY/MID-ATLANTIC WED/THURS
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE GUIDANCE SHOWS A STRONG PACIFIC SHORTWAVE CURRENTLY CROSSING  
BRITISH COLUMBIA THAT WILL DIGGING SOUTHEASTWARD OVER THE NEXT 48  
HOURS AND AMPLIFY ACROSS THE UPPER MIDWEST/OH VALLEY AND  
MID-ATLANTIC REGION. AN ASSOCIATED CLIPPER-TYPE SURFACE LOW WILL  
CROSS THE REGION AND THEN QUICKLY EJECT OFFSHORE SOUTHERN NEW  
ENGLAND ON THURSDAY. THE 12Z CMC TRENDED A BIT FASTER AND IS CLOSE  
TO THE MODEL CONSENSUS WITH THIS SYSTEM. THEREFORE...A GENERAL  
MODEL BLEND WILL BE PREFERRED CONSIDERING THE GUIDANCE IS RATHER  
WELL CLUSTERED.  
 
   
..SHORTWAVE DIGGING SOUTH ACROSS THE PLAINS THURS
 
   
..ENERGY CROSSING THE LOWER MS/TN VALLEYS ON FRI
 
   
..POSSIBLE SURFACE LOW DEVELOPMENT OFF THE MID-ATLANTIC ON FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A SHORTWAVE CRESTING THE TOP OF THE WESTERN NORTH AMERICA RIDGE  
AXIS WILL DROP SOUTH DOWN FROM THE NORTHWEST TERRITORIES IN CANADA  
AND THEN DOWN ACROSS THE PLAINS THURSDAY BEFORE SWEEPING ACROSS  
THE LOWER MS AND TN VALLEY REGION ON FRIDAY. THIS ENERGY IS  
EXPECTED TO HELP RELOAD A LARGER SCALE LONGWAVE TROUGH ACROSS THE  
EASTERN U.S. BY THE END OF THE WEEK AND WILL ENCOURAGE A SURFACE  
LOW DEVELOPING OFFSHORE THE MID-ATLANTIC AS WELL. THE 12Z CMC IS  
NOW THE SLOWEST AND STRONGEST MODEL WITH THIS FEATURE...WITH THE  
REMAINING GUIDANCE RATHER WELL CLUSTERED TOWARD A SOMEWHAT MORE  
PROGRESSIVE AND FLATTER SOLUTION. HOWEVER...THE 12Z NAM IS ALSO ON  
THE SLOW AND SOMEWHAT DEEPER SIDE WITH THE SHORTWAVE. ALL OF THE  
MODELS SUPPORT AT LEAST A WEAK SURFACE WAVE OFFSHORE THE  
MID-ATLANTIC BY THE END OF THE PERIOD...BUT WITH THE SHORTWAVE  
ENERGY GENERALLY SHEARING OUT...THE SURFACE WAVE SHOULD TEND TO BE  
ELONGATED AND MAY ACTUALLY TAKE THE FORM OF MULTIPLE WAVES. THE  
12Z CMC IS AN OUTLIER WITH ITS STRONGER SOLUTION NEAR THE VA CAPES  
AT THE END OF THE PERIOD. WILL PREFER A CONSENSUS OF THE FLATTER  
12Z GFS/12Z UKMET AND 12Z ECMWF AT THIS TIME.  
 
   
..NEW UPPER LOW DROPPING SOUTH TOWARD THE GREAT LAKES BY FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE MODELS TAKE ARCTIC SHORTWAVE ENERGY CURRENTLY UP OVER NUNAVUT  
IN NORTHERN CANADA DOWN TO THE SOUTH OVER THE NEXT COUPLE OF DAYS  
WHICH RESULTS IN A NEW UPPER LOW DROPPING SOUTH OVER HUDSON BAY  
AND THEN ACROSS ONTARIO BY THE END OF THE WEEK. THIS WILL RESULT  
IN HEIGHT FALLS ENCROACHING ON THE GREAT LAKES REGION AND A WAVE  
OF LOW PRESSURE IMPACTING THIS REGION. THE 12Z NAM DIGS THE ENERGY  
FARTHEST SOUTH AND CROSSING THE UPPER GREAT LAKES...WITH THE 12Z  
CMC NOW A BIT SLOWER AND KEEPING MORE ENERGY BACK OVER WESTERN  
ONTARIO. THE 12Z GFS/12Z UKMET AND 12Z ECMWF ALL TEND TO CLUSTER  
TOGETHER WELL OVER CENTRAL ONTARIO BY THE END OF THE PERIOD AND  
HAVE GOOD SUPPORT FROM THE 12Z GEFS MEAN AND 00Z ECENS MEAN. THUS  
WILL PREFER A BLEND OF THE GFS/UKMET AND ECMWF.  
 
   
..SHORTWAVE TROUGH ARRIVING ACROSS THE PACIFIC NORTHWEST ON FRI
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS AND 12Z UKMET  
CONFIDENCE: AVERAGE  
 
THE MODELS BREAK DOWN THE WESTERN NORTH AMERICA RIDGE BY THE END  
OF THE WEEK AND THIS ALLOWS A SHORTWAVE TROUGH AND ASSOCIATED COLD  
FRONT TO ARRIVE ACROSS THE PACIFIC NORTHWEST BY THE END OF THE  
WEEK. THE 12Z CMC AND 12Z ECMWF ARE BOTH GENERALLY THE SLOWEST  
SOLUTIONS WITH THIS SYSTEM. THE 12Z NAM/12Z GFS AND 12Z UKMET ARE  
ALL MORE PROGRESSIVE WHICH IS SUPPORTED BY THE 00Z ECENS MEAN AND  
12Z GEFS MEAN. HOWEVER...THE NAM MAY BE SLOWING DOWN THE NORTHERN  
PORTION OF THE TROUGH AXIS A BIT TOO MUCH BY THE END OF THE PERIOD  
OVER WESTERN CANADA. WILL LEAN TOWARD THE MORE PROGRESSIVE  
CONSENSUS WITH A BLEND OF THE GFS AND UKMET.  
 
   
..UPPER LEVEL LOW OVER THE BAJA PENINSULA/GULF OF CALIFORNIA
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/12Z UKMET AND 12Z ECMWF  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
THE 12Z NAM IS A WESTERLY OUTLIER WITH THE EVOLUTION OF THE UPPER  
LOW OVER THE BAJA PENINSULA AS IT TAKES THE UPPER LOW SOUTH  
THROUGH THE PERIOD...AND WELL WEST OF THE GLOBAL MODELS. THE WELL  
CLUSTERED GFS/UKMET AND ECMWF SOLUTIONS TAKE THE UPPER LOW MORE  
SOUTHEAST AND DOWN OVER NORTHWEST MAINLAND MEXICO. THE 12Z GEFS  
MEAN AND 00Z ECENS MEAN NOW SUPPORT THIS CONSENSUS...AND THUS WILL  
PREFER A BLEND OF THE GFS/UKMET AND ECMWF SOLUTIONS.  
 
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page