369  
FXUS10 KWNH 240642  
PMDHMD  
 
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
241 AM EDT MON APR 24 2017  
 
VALID APR 24/0000 UTC THRU APR 27/1200 UTC  
 
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
 
00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE INTERVALS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE ITS SHORT  
RANGE FORECAST.  
 
SYSTEM MOVING INTO THE WEST WEDNESDAY  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
THE GUIDANCE SHOWS GOOD AGREEMENT WITH THE SYSTEM MOVING INTO THE  
WEST WEDNESDAY. A COMPROMISE OF THE AVAILABLE GUIDANCE -- SIMILAR  
TO THE PARALLEL VERSION OF THE NATIONAL BLEND OF MODELS -- LOOKS  
GOOD HERE TO DEAL WITH ANY LINGERING DETAIL ISSUES WITH ABOVE  
AVERAGE CONFIDENCE.  
 
QUASI-PHASED SYSTEM MOVING ACROSS THE WEST INTO THE PLAINS  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: CANADIAN/ECMWF COMPROMISE  
CONFIDENCE: BELOW AVERAGE  
 
THE GUIDANCE HAS SHOWN MARKED CHANGES SINCE THIS TIME YESTERDAY,  
GENERALLY SHOWING A SLIGHTLY SLOWER AND MORE CLOSED SOLUTION. THE  
00Z GFS USES CONVECTIVE/GRIDSCALE FEEDBACK BULL'S EYES TO DRAG ITS  
NORTHERN STREAM TROUGH TOO QUICKLY INTO THE GREAT LAKES AND  
DEFINES THE NORTHEAST SIDE OF THE 12Z GLOBAL ENSEMBLE SPREAD. THE  
GLOBAL ENSEMBLE SPREAD HERE IS GREATER THAN AVERAGE, REFLECTING  
WHAT WE NORMALLY SEE AT THE 5+ DAY RANGE DURING DAY 3. ALL THE  
DETERMINISTIC GUIDANCE DEFINES THE BOUNDARIES SET BY THE 12Z  
GLOBAL ENSEMBLE SPREAD -- NOTHING IS IDEAL. A STRONGER VERSION OF  
THE 00Z ECMWF ALOFT, WITH A SOMEWHAT MORE WESTERLY SURFACE LOW  
LYING BETWEEN THE 00Z CANADIAN AND 00Z ECMWF, IS AS GOOD AS IT  
GETS, AND IS PREFERRED WITH BELOW AVERAGE CONFIDENCE.  
 
DEEP SYSTEM MOVING UP THE EAST COAST  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: NON-NAM COMPROMISE  
CONFIDENCE: ABOVE AVERAGE  
 
THE 00Z NAM IS LAGGING IN THE RECURVATURE OF THIS SYSTEM, PERHAPS  
DUE TO ITS STRONGER RIDGE IN SOUTHEAST CANADA. SINCE THE OTHER  
GUIDANCE LIES BETWEEN THE 18Z GEFS MEAN AND 12Z ECMWF ENSEMBLE  
MEAN, FAVOR A NON-NAM COMPROMISE (00Z GFS, 00Z CANADIAN, 00Z  
UKMET, AND 00Z ECMWF) WITH ABOVE AVERAGE CONFIDENCE.  
 
WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... /ALL LOWER CASE/  
WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... /ALL LOWER CASE/  
 
ROTH  

 
 
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