061  
FXUS10 KWNH 091610  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1109 AM EST SAT DEC 09 2017  
 
VALID DEC 09/1200 UTC THRU DEC 13/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
ERRORS WITHIN THE GFS/NAM INITIALIZATIONS DO NOT SEEM TO DEGRADE  
THEIR SHORT RANGE FORECASTS.  
 
 
SYSTEM SIDESWIPING THE PACIFIC NORTHWEST MONDAY AFTERNOON  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-GFS BLEND; CONFIDENCE AVERAGE  
 
THE 12Z GFS/TO SOME DEGREE THE 12Z NAM WAS QUICKER THAN THE OTHER  
GUIDANCE MOVING THIS SYSTEM THROUGH WESTERN CANADA INTO ALBERTA BY  
LATE TUESDAY. THE SLOWER GUIDANCE IS CLOSER TO THE 06Z GEFS/00Z  
ECMWF ENSEMBLE MEAN SOLUTIONS. HOWEVER, THE 00Z ECMWF LOOKS TOO  
STRONG IN MAINTAINING A CLOSED LOW MOVING OVER THE TOP OF THE  
RIDGE -- IT SHOULD END UP WEAKER DUE TO THE SUPERGEOSTROPHIC FLOW  
IN THE REGION. IT SHOULD PROBABLY MOVE ON A MORE NORTHERLY  
TRAJECTORY AS WELL BASED ON THE POSITION OF THE NORTHERNMOST  
EXTENT OF THE RIDGE NORTH OF AK. A COMPROMISE OF THE 00Z ECMWF,  
00Z UKMET, AND 00Z CANADIAN IS PREFERRED WITH AVERAGE CONFIDENCE.  
 
UPPER LOW PARKING ACROSS NORTHWEST MEXICO MONDAY ONWARD  
SECOND STRONGER CLIPPER MOVING ACROSS GREAT LAKES MON/TUE  
CLIPPER DIVING INTO THE UPPER MIDWEST SUNDAY  
SYSTEM MOVING BY THE NORTHEAST TODAY/SUNDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS. A  
COMPROMISE OF THE 12Z GFS, 12Z NAM, 00Z ECMWF, 00Z UKMET, AND 00Z  
CANADIAN IS PREFERRED TO DEAL WITH LINGERING DETAIL ISSUES WITH  
ABOVE AVERAGE CONFIDENCE.  
 
ROTH  
 
PREVIOUS MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
PREVIOUS 500 MB FORECASTS AT  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 

 

 
 
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