920  
FXUS10 KWNH 231831  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
230 PM EDT MON OCT 23 2017  
 
VALID OCT 23/1200 UTC THRU OCT 27/0000 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
12Z MODEL PREFERENCES WITH CONFIDENCE INTERVALS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT  
RANGE FORECASTS.  
 
FAST MOVING SYSTEM DIGGING INTO MN LATE THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: GFS/UKMET BLEND; CONFIDENCE AVERAGE  
 
A STRONG CLOSED HIGH OFFSHORE THE PACIFIC NORTHWEST SHOULD LEAD TO  
AN AMPLIFYING TROUGH MID-CONTINENT. THIS ARGUES AGAINST THE MORE  
OPEN/PROGRESSIVE 00Z CANADIAN, A MORE NORTHERLY 12Z NAM, AND THE  
SLOWER/LESS DUG IN 12Z ECMWF. A COMPROMISE OF THE 12Z GFS AND 12Z  
UKMET IS CLOSE TO A COMPROMISE OF THE 12Z GEFS/00Z ECMWF ENSEMBLE  
MEAN COMPROMISE, WHICH IS PREFERRED WITH AVERAGE CONFIDENCE AS  
MODEL SPREAD HAS INCREASED WITH THIS SYSTEM.  
 
MERGING SYSTEMS NEAR THE GREAT LAKES MONDAY NIGHT  
EJECTING EASTERN TROUGH THURSDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z ECMWF/12Z UKMET BLEND; CONFIDENCE BELOW AVE  
 
THE GUIDANCE IS QUITE AGREEABLE UNTIL TUESDAY MORNING. ON  
WEDNESDAY, THE 12Z NAM/12Z CANADIAN/12Z ECMWF BECOME LOW/DEEP  
ALOFT WITH THE MAIN SYSTEM, DECIDEDLY SLOWER THAN THE 00Z  
ECMWF/12Z GEFS ENSEMBLE MEANS. HOWEVER, THE 12Z GFS OUTPACES ITS  
06Z ENSEMBLE MEAN BY THEN. SINCE LARGE SPREAD REMAINS, WILL STAY  
RELATIVELY CLOSE TO THE PREVIOUS PREFERENCE AND PREFER A 00Z  
ECMWF/12Z UKMET COMPROMISE HERE. CONSIDERING THE MODEL SPREAD AND  
POSSIBLE SYSTEM ACCELERATION, CONFIDENCE IS BELOW AVERAGE HERE.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML  
 
ROTH  

 
 
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