916  
FXUS10 KWNH 301846  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
245 PM EDT MON OCT 30 2017  
 
VALID OCT 30/1200 UTC THRU NOV 03/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..NEGATIVE TILT TROUGH CROSSING THE NORTHEAST
 
   
..DEEP SURFACE LOW EXITING INTO SOUTHEAST CANADA
 
   
..MERGING WITH NORTHERN STREAM CLOSED LOW OVER UPPER MIDWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE LATEST MODELS HAVE COME INTO VERY GOOD AGREEMENT WITH THE  
DETAILS OF THE EXITING NEGATIVELY TILTED TROUGH CURRENTLY CROSSING  
THE NORTHEAST. ALL OF THIS ENERGY ALONG WITH THE AN ATTENDANT DEEP  
SURFACE LOW CROSSING THE ST LAWRENCE RIVER VALLEY THIS MORNING  
WILL LIFT NORTH ACROSS QUEBEC THROUGH TUESDAY WHILE BEING CAPTURED  
BY THE CLOSED NORTHERN STREAM LOW CENTER CURRENTLY OVER THE UPPER  
MS VALLEY AND UPPER GREAT LAKES REGION. A GENERAL MODEL BLEND WILL  
BE PREFERRED AT THIS TIME GIVEN THE STRONG MASS FIELD AGREEMENT  
WITH THESE FEATURES.  
 
   
..SHORTWAVE OVER THE SOUTHWEST SHEARING EAST TOWARD WEST TX
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
A COMPACT MID LEVEL LOW CENTER AND ASSOCIATED TROUGH OVER THE  
SOUTHWEST WILL EJECT EAST AND GRADUALLY SHEAR OUT THROUGH TUESDAY  
TOWARD WEST TX AS IT ENCOUNTERS LARGER SCALE CONFLUENT FLOW ALOFT.  
A GENERAL MODEL BLEND WILL BE PREFERRED.  
 
   
..SHORTWAVE OVERTOPPING THE GULF OF AK RIDGE AXIS
 
   
..ENERGY SETTLING SOUTHEAST ACROSS THE DAKOTAS/UPPER MIDWEST
 
   
..DEEP/BROAD SURFACE WAVE SLIDING DOWN CANADIAN ROCKIES
 
   
..SURFACE WAVE EJECTING ACROSS UPPER MIDWEST/GREAT LAKES
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF  
CONFIDENCE: AVERAGE  
 
THE MODELS TAKE AN UPPER LOW AND ASSOCIATED SHORTWAVE TROUGH  
ACROSS AREAS OF SOUTHWEST AK THROUGH TONIGHT AND EARLY TUESDAY AS  
IT TOPS AND GRADUALLY BREAKS DOWN THE STRONG GULF OF AK RIDGE  
AXIS. A PORTION OF THIS ENERGY ALONG WITH A LEAD SHORTWAVE AHEAD  
OF IT WILL GRADUALLY LEAD TO A MID LEVEL TROUGH EVOLUTION ACROSS  
THE NORTHERN PLAINS AND UPPER MIDWEST THROUGH WEDNESDAY BEFORE THE  
ENERGY THEN CROSSES THE GREAT LAKES AND THEN EXITS BY LATER  
THURSDAY ACROSS ONTARIO. A STRONG SURFACE LOW ACCOMPANYING THE  
DIGGING SECONDARY SHORTWAVE ENERGY WILL SLIDE SOUTHEAST DOWN THE  
EAST SIDE OF THE CANADIAN ROCKIES AND CROSS THE NORTHERN PLAINS  
AND UPPER MIDWEST AS A TRAILING COLD FRONT GRADUALLY SETTLES DOWN  
TOWARD THE SOUTHERN PLAINS. THE 12Z UKMET BY WEDNESDAY BECOMES A  
BIT MORE PROGRESSIVE WITH THE EVOLUTION OF THE ENERGY OVER THE  
NORTHERN PLAINS AND SUGGESTS A FASTER SURFACE LOW/COLD FRONT  
EVOLUTION. THE UKMET THOUGH HAS AT LEAST TRENDED A BIT SLOWER WITH  
THIS CYCLE. THE 12Z GFS AND 12Z CMC ARE A LITTLE SLOWER THAN THE  
UKMET...AND THE 12Z NAM AND 12Z ECMWF ARE THE SLOWEST AT LEAST  
THOUGH WEDNESDAY. THE GFS APPEARS TO BE A TAD TOO STRONG WITH ITS  
ENERGY AND CORRESPONDING SURFACE LOW CROSSING SOUTHERN MANITOBA  
AND THE DAKOTAS RESPECTFULLY THROUGH WEDNESDAY. TOWARD THE LATER  
PART OF THE PERIOD...THE CMC/GFS AND ECMWF COME INTO BETTER MASS  
FIELD AGREEMENT...WITH THE NAM TAKING ITS SURFACE LOW NORTH OF THE  
MODEL CONSENSUS...
AND THE UKMET AGAIN APPEARING TO BE TOO  
PROGRESSIVE. BASED ON THE LATEST DETERMINISTIC MODEL SPREAD AND  
ENSEMBLE CLUSTERING...A BLEND OF THE GFS AND ECMWF WILL BE  
PREFERRED.  
 
   
..AMPLIFYING UPPER LOW NEAR VANCOUVER ISLAND BY THURSDAY
 
   
..ASSOCIATED SURFACE LOW JUST OFF THE PACIFIC NORTHWEST
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: NON-CMC CONSENSUS  
CONFIDENCE: ABOVE AVERAGE  
 
A PORTION OF THE WEAKENING COMPACT UPPER LOW/TROUGH MOVING INTO  
SOUTHWEST AK OVER TOP THE RIDGE WILL DIG DUE SOUTH THROUGH  
WEDNESDAY AND THEN RE-AMPLIFY INTO A CLOSED LOW CENTER OVER  
SOUTHERN BRITISH COLUMBIA NEAR VANCOUVER ISLAND THROUGH THURSDAY.  
THIS WILL LEAD TO A WELL-DEFINED SURFACE LOW JUST OFF THE WA COAST  
BY THE END OF THE PERIOD WHICH WILL BE ENHANCING THE WESTERLY  
ONSHORE FLOW INTO THE COASTAL RANGES. THE 12Z CMC APPEARS TO PLACE  
ITS UPPER LOW PERHAPS A TAD TOO FAR WEST BY THE END OF THE PERIOD  
WITH ATTEMPT AT SOME RETROGRESSION AROUND THE SOUTHEAST FLANK OF A  
NEW UPPER RIDGE BUILDING OVER THE ALEUTIANS. THE REMAINING  
GUIDANCE IS IN GOOD AGREEMENT AND SO A NON-CMC CONSENSUS WILL BE  
PREFERRED AT THIS TIME.  
 
   
..SOUTHERN STREAM SHORTWAVE CROSSING SOUTHERN PLAINS THURSDAY
 
   
..INTERACTING WITH SURFACE FRONT NEAR THE RED RIVER VALLEY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
PREFERENCE: BLEND OF THE 12Z GFS/ECMWF  
CONFIDENCE: AVERAGE  
 
THE MODELS TAKE A SOUTHERN STREAM SHORTWAVE TROUGH ACROSS THE  
SOUTHERN PLAINS BY THURSDAY WHICH WILL BE INTERACTING WITH A COLD  
FRONT SETTLING SOUTHWARD DOWN ACROSS THE RED RIVER VALLEY. A WAVE  
OF LOW PRESSURE WILL DEVELOP ALONG THIS BOUNDARY AND LIKELY BE  
FOCUSED JUST NORTH OF THE RED RIVER. THE 12Z UKMET APPEARS TO BE A  
TAD TOO FAR SOUTH...WITH THE 12Z NAM TOO FAR NORTH...ALTHOUGH THE  
NAM DOES COME INTO ALIGNMENT WITH THE MODEL CONSENSUS BY THE END  
OF THE PERIOD. THE 12Z GFS AND 12Z ECMWF SOLUTIONS ARE MUCH BETTER  
CLUSTERED IN BETWEEN...AND A BLEND OF THESE SOLUTIONS WILL BE  
PREFERRED.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ORRISON  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page