863  
FXUS10 KWNH 251852  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
252 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 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 12Z UKMET. WHILE IT IS NOW VERY CLOSE TO MODEL CONSENSUS  
IN ITS POSITION OF THE SECONDARY SURFACE LOW THAT DEVELOPS NEAR  
THE GULF OF MAINE...IT IS STILL MUCH DEEPER THAN THE OTHER MODELS.  
THIS WAS ALSO THE CASE ON THE 00Z MODEL CYCLE...SO A NON-UKMET  
BLEND IS STILL PREFERRED.  
 
CHANGE FROM THE PRELIMINARY PREFERENCE: NONE. THE UKMET HAS MOVED  
CLOSER TO THE OTHER MODELS IN ITS POSITION OF THE EVENTUAL SURFACE  
LOW...BUT THE INTENSITY IS MUCH STRONGER.  
 
   
..SHORTWAVE TROUGH DIGGING FROM THE CANADIAN PRAIRIES TODAY
 
TO  
THE WESTERN GREAT LAKES BY FRIDAY...   
..ASSOCIATED TROUGH AMPLIFICATION AND CYCLONE DEVELOPMENT
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: AVERAGE  
 
THE MODELS ARE NOW IN MUCH BETTER AGREEMENT WITH THE MASS FIELDS  
ASSOCIATED WITH THIS DEVELOPING CYCLONE AS COMPARED TO THE  
PREVIOUS (00Z) MODEL CYCLE. THE NEW 12Z ECMWF HAS TRENDED IN THE  
DIRECTION OF THE 12Z NAM... GFS... AND UKMET. THESE MODELS  
GENERALLY SHOW A FASTER OCCLUSION OF THE CYCLONE...WITH THE  
EVENTUAL WEAKENING CYCLONE AND ASSOCIATED TROUGH LIFTING NORTHEAST  
FASTER AS THE WEEKEND APPROACHES. THE 12Z CMC REMAINS CLOSE TO ITS  
PREVIOUS SOLUTION (AND THAT OF THE 00Z ECMWF AND 00Z ECMWF  
ENSEMBLE MEAN). THIS SHOWED A SLOWER DEVELOPMENT OF THE CYCLONE  
INITIALLY...AND A SLOWER EJECTION TO THE NORTHEAST LATER ON FRIDAY  
AND INTO SATURDAY. GIVEN THE PRIOR SUPPORT OF THE ECMWF ENSEMBLE  
MEMBERS FOR THIS SOLUTION...AND THE INITIAL PREFERENCE FOR THAT  
SOLUTION...THE 12Z CMC WILL BE INCLUDED IN THE PREFERENCE FOR THIS  
SYSTEM WHICH IS NOW TRENDED TO A GENERAL MODEL BLEND. THIS WILL  
HELP CAPTURE SOME OF THE REMAINING UNCERTAINTY AS THE NEWER 12Z  
ECMWF ENSEMBLE IS NOT YET IN. OVERALL THOUGH...EVEN WITH THE  
DIFFERENCES SHOWN BY THE CMC...THE MODELS STILL SHOW FAIRLY  
SIMILAR SOLUTIONS.  
 
CHANGE FROM THE PRELIMINARY PREFERENCE: TREND TOWARD A GENERAL  
BLEND (REASONING IS DISCUSSED ABOVE).  
 
...TROPICAL WAVE/DISTURBANCE CURRENTLY IN THE WESTERN CARIBBEAN  
AND APPROACHING THE FLORIDA STRAITS BY THIS WEEKEND...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: BLEND OF 12Z ECMWF AND 12Z GFS  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
A BROAD AREA OF LOW PRESSURE WAS SITUATED OVER THE WESTERN  
CARIBBEAN SEA AND CENTRAL AMERICA...AND MODELS SHOW THIS SLOWLY  
CONSOLIDATING OVER THE NEXT COUPLE DAYS. NHC AND TAFB HAVE  
ANALYZED THE CENTER VERY CLOSE TO THE COAST OF CENTRAL  
AMERICA...AND THE 12Z GFS AND 12Z ECMWF ARE CLOSEST TO THAT  
REPRESENTATION (FURTHEST WEST). THROUGH SATURDAY...THE GFS AND  
ECMWF REMAIN ON THE WESTERN END OF MODEL SPREAD AND ARE ALSO  
GENERALLY WEAKER WITH THE SURFACE LOW. THE 12Z UKMET IS BY FAR THE  
STRONGEST...AND SEEMS TOO FAR EAST AND STRONG GIVEN THE INITIAL  
CONDITIONS.  
 
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