231  
FXUS10 KWNH 110504  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
103 AM EDT WED OCT 11 2017  
 
VALID OCT 11/0000 UTC THRU OCT 14/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z PRELIMINARY MODEL EVALUATION...INCLUDING PREFERENCES/CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
 
...TROUGH DEAMPLIFYING AND ACCELERATING TO THE NORTHEAST U.S.  
COAST BY THURSDAY AND ACCOMPANYING WEAK SURFACE LOW IN THE UPPER  
MIDWEST / OHIO VALLEY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
IN GENERAL...THERE IS EXCELLENT MODEL AGREEMENT WITH THIS SYSTEM.  
THE EXCEPTION IS THE 12Z CMC WHICH SHOWS HIGHER HEIGHTS THROUGH  
THE DEPTH OF THE RIDGE OVER MUCH OF THE EASTERN CONUS. THIS LEADS  
TO A FASTER EJECTION AND DEAMPLIFICATION OF THE WAVE THAN ALMOST  
ALL OTHER MODELS...AND THE RIDGE BUILDING IN ACROSS THE EASTERN  
U.S. FASTER. THEREFORE...A NON-CMC BLEND IS RECOMMENDED FOR THIS  
SYSTEM WITH ABOVE AVERAGE CONFIDENCE.  
 
...UPPER TROUGH ARRIVING IN THE NORTHWESTERN U.S. WITH LEAD  
SHORTWAVE EJECTING TO HUDSON BAY BY THE WEEKEND...  
...ATTENDANT SURFACE CYCLONE DEVELOPING INTO CANADA AND ASSOCIATED  
COLD FRONT CROSSING THE NW REACHING NRN PLAINS ON THURSDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
MODELS HAVE CONTINUED TO COME INTO BETTER AGREEMENT WITH THIS  
SYSTEM...AND ARE VERY CLOSE IN THE PLACEMENT OF THE SURFACE  
CYCLONE...TIMING OF THE WAVE AS IT EJECTS...AND THE COLD FRONT. A  
GENERAL MODEL BLEND IS RECOMMENDED WITH ONLY SOME MINOR DETAIL  
DIFFERENCES NOTED.  
 
...SECONDARY SHORTWAVE DIGGING SOUTH INTO THE WESTERN U.S. FROM  
LATE THURSDAY INTO FRIDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: SLIGHTLY ABOVE AVERAGE  
 
WHILE THERE IS SLIGHTLY LESS MODEL AGREEMENT WITH THIS SYSTEM AS  
COMPARED TO THE OTHERS...THE MODELS ARE STILL FAIRLY CONSISTENT  
WITH THEIR MASS FIELDS. THEY ALL HAVE A SIMILAR TIMING FOR THIS  
WAVE AS IT DROPS SOUTH ON THE BACK PERIPHERY OF THE WESTERN U.S.  
TROUGH...A SIMILAR STRUCTURE TO THE TROUGH AS IT AMPLIFIES IN  
RESPONSE TO THE DIGGING WAVE ON FRIDAY...AND EVEN SIMILAR  
PLACEMENT OF VORT MAXES ALOFT. THE 12Z CMC DID SHOW A WEAKER  
TROUGH OVERALL WITH HIGHER HEIGHTS OVER MUCH OF THE WEST...AND A  
FASTER EJECTION OF THE WAVE INTO SATURDAY. GIVEN THAT THE 12Z CMC  
SEEMED TO BE A BIT HIGH WITH ITS HEIGHT FIELDS THROUGHOUT THE  
CONUS IN THE 12Z RUN...A NON-CMC BLEND IS RECOMMENDED.  
 
...TROPICAL WAVE CURRENTLY NEAR HISPANIOLA MOVING WEST TO NEAR  
FLORIDA BY FRIDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-CMC BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
FOR THE CURRENT DEPICTION OF HEIGHT FIELDS ACROSS THE GULF OF  
MEXICO...CARIBBEAN SEA...AND SW ATLANTIC OCEAN...THE 12Z CANADIAN  
SHOWS A STRONGER SUBTROPICAL RIDGE AND WEAKER MID-UPPER LEVEL LOW  
ASSOCIATED WITH THE WAVE. THIS EVENTUALLY LEADS TO A SLOWER  
WESTWARD PROGRESSION OF THE WAVE BY FRIDAY. THE CANADIAN ALSO  
DEVELOPS A SURFACE LOW FAR TO THE NORTHWEST (NEAR 28N/74W BY 12Z  
FRIDAY) WHICH IS A SIGNIFICANT OUTLIER FROM THE OTHER MODEL  
SOLUTIONS. OTHERWISE...THERE ARE SOME DETAIL DIFFERENCES BETWEEN  
THE MODELS BUT THEY ARE ALL CLOSE ENOUGH TO BE USED IN A GENERAL  
BLEND OTHERWISE. THEREFORE...A NON-CMC BLEND IS RECOMMENDED FOR  
THIS SYSTEM.  
 
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WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
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