633  
FXUS10 KWNH 171828  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
228 PM EDT TUE OCT 17 2017  
 
VALID OCT 17/1200 UTC THRU OCT 21/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z FINAL MODEL EVALUATION WITH FINAL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT  
RANGE FORECASTS.  
 
...UPPER TROUGH DIGGING INTO THE PACIFIC NORTHWEST WEDNESDAY NIGHT  
WITH ASSOCIATED ATMOSPHERIC RIVER EVENT...   
..TROUGH/COLD FRONT REACHING THE PLAINS ON FRIDAY
 
 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM / 12Z ECMWF BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
DIFFERENCES IN THE GUIDANCE ARE MINOR UNTIL THE UPPER TROUGH AXIS  
MOVES OVER THE INTERMOUNTAIN WEST ON FRI. ENSEMBLES HAVE BEEN  
TRENDING SLIGHTLY FASTER WITH THE UPPER TROUGH AXIS VALID FRIDAY  
EVENING BUT THE 12Z GFS IS AT THE FAR LEADING EDGE OF THE LATEST  
ENSEMBLE GUIDANCE...AND IS CONSIDERED TOO FAST. ONLY MINOR  
ADJUSTMEMNTS WERE SEEN IN THE 12Z ECWFM/UKMET/CMC FOR THIS  
SYSTEM...WITH THE 12Z GFS REMAINING FASTER. UPSTREAM FLOW IS  
AMPLIFYING SO FASTER SOLUTIONS LIKE THE GFS ARE LESS PREFERRED. A  
SOLUTION TOWARD THE MIDDLE OF THE LATEST ENSEMBLE  
GUIDANCE...REPRESENTED BY A 12Z NAM / 12Z ECMWF BLEND IS  
RECOMMENDED HERE.  
 
...SHORTWAVE MOVING QUICKLY ALONG THE U.S.-CANADA BORDER THROUGH  
THU WITH ASSOCIATED DEEPENING SURFACE LOW AND COLD FRONT...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENEARL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS ARE IN BETTER AGREEMENT WITH THE 12Z UKMET A LITTLE  
FASTER COMPARED TO ITS 00Z RUN AND IN BETTER ALIGNMENT WITH THE  
REMAINING DETERMINISTIC GUIDANCE. THE ENSEMBLE MEANS SHOW GOOD  
AGREEMENT WITH THE 12Z DETERMINISTIC CONSENSUS SO A GENERAL MODEL  
BLEND IS RECOMMENDED.  
 
...UPPER LEVEL TROUGH AXIS CROSSING THE SRN ROCKIES INTO THE  
PLAINS ON FRIDAY...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z GFS/12Z ECMWF BLEND  
CONFIDENCE: AVERAGE  
 
MINOR AMPLITUDE/TIMING DIFFERENCES EXIST WITH THIS SYSTEM...WITH A  
12Z GFS AND 00Z ECMWF BLEND DOWN THE MIDDLE OF THESE DIFFERENCES.  
 
...LINGERING BROAD TROUGH OVER THE SOUTHEAST STATES WITH SLOW  
MOVING COLD FRONT IN THE VICINITY OF FLORIDA...  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GENERAL MODEL BLEND  
CONFIDENCE: ABOVE AVERAGE  
 
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
OTTO  
 

 
 
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