565  
FXUS10 KWNH 251709  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
109 PM EDT WED OCT 25 2017  
 
VALID OCT 25/1200 UTC THRU OCT 29/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL EVALUATION...WITH PRELIMINARY PREFERENCES AND CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...INCREASINGLY NEGATIVE TILT SHORTWAVE TROUGH EJECTING INTO THE  
NORTHEAST AND THEN DEAMPLIFYING OVER EASTERN CANADA...   
..SECONDARY SURFACE LOW DEVELOPMENT NEAR THE GULF OF MAINE
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-UKMET BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
MODELS ARE IN GOOD AGREEMENT OVERALL WITH THE EVOLUTION OF THIS  
SYSTEM...SHOWING SIMILARITY IN THEIR MASS FIELDS AND EVEN OTHER  
FIELDS SUCH AS THE DISTRIBUTION OF QPF. THIS LEADS TO HIGHER  
CONFIDENCE IN A MODEL CONSENSUS. THE MOST NOTABLE DIFFERENCE IS  
WITH THE 00Z UKMET. AS THE NEGATIVE TILT TROUGH EJECTS...MOST  
MODELS KEEP THE STRONGEST MID-LEVEL VORTICITY CONCENTRATED IN THE  
BASE OF THE TROUGH...WHILE THE UKMET MIGRATES IT AROUND THE TROUGH  
MORE QUICKLY...LEADING TO A STRONGER SURFACE LOW THAT IS DISPLACED  
FURTHER TO THE NORTHWEST OF THE OTHER MODELS IN QUEBEC BY FRIDAY.  
GIVEN THE LACK OF SUPPORT FROM OTHER MODELS...A NON-UKMET BLEND IS  
PREFERRED FOR THIS SYSTEM.  
 
   
..SHORTWAVE TROUGH DIGGING FROM THE CANADIAN PRAIRIES TODAY
 
TO  
THE WESTERN GREAT LAKES BY FRIDAY...   
..ASSOCIATED TROUGH AMPLIFICATION AND CYCLONE DEVELOPMENT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 00Z ECMWF / 00Z CMC  
WEIGHTED TOWARD THE ECMWF (65-70 PERCENT)  
CONFIDENCE: AVERAGE  
 
SMALL BUT IMPORTANT DIFFERENCES EXIST WITH THIS SYSTEM...WHICH  
WILL AFFECT THE DISTRIBUTION OF PRECIPITATION ACROSS THE WESTERN  
GREAT LAKES REGION. THE 12Z GFS AND 12Z NAM ARE JOINED BY THE 00Z  
UKMET IN SHOWING A STRONGER CYCLONE OVERALL BY FRIDAY  
AFTERNOON...AND THE THE ASSOCIATED LOW LIFTING FASTER TO THE  
NORTHEAST. THIS IS LIKELY DUE TO A FASTER OCCLUSION OF THE LOW AND  
SUBSEQUENT WEAKENING OF THE SYSTEM. THE 00Z ECMWF AND 00Z  
CMC...HOWEVER...SHOW A SLOWER PROGRESSION WITH A WEAKER CYCLONE  
OVERALL (BUT STILL DEPICTING A CLOSED LOW IN THE MID LEVELS).  
UNSURPRISINGLY THE SOLUTIONS WITH A STRONGER CYCLONE SHOW  
ACCOMPANYING STRONGER COLD AIR ADVECTION ON THE BACK SIDE OF THE  
LOW...AND COLDER LOW-MID LEVEL TEMPERATURES NEAR AND NORTHWEST OF  
THE SURFACE LOW.  
 
THE PRELIMINARY PREFERENCE IS TOWARD THE 00Z ECMWF AND 00Z  
CMC...WHICH ALSO HAVE FAIRLY GOOD SUPPORT FROM THE ECMWF ENSEMBLE  
MEMBERS. THE SLIGHTLY WARMER SOLUTIONS MAY GIVE MORE REALISTIC  
TEMPERATURE PROFILES FOR AN EARLY SEASON STORM THAT MAY PRODUCE  
WINTRY PRECIP...AND THE WARMER TEMPERATURES MAY BETTER FIT THE  
INTENSITY OF THE SURFACE LOW...WHICH IS ABOVE 1000MB ON EVEN THE  
STRONGER MODEL SOLUTIONS AT THIS POINT.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
LAMERS  
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab HPC Page Main Text Page