MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 246 PM EDT TUE JUL 28 2015 VALID JUL 28/1200 UTC THRU AUG 01/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH ANALYSIS AND FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO AFFECT SHORT TERM FORECAST ERRORS STRONG UPPER TROUGH CROSSING THE DAKOTAS ON TUE REACHING JAMES BAY BY FRIDAY WITH ATTENDANT COLD FRONT CROSSING THE MID-MISS VALLEY EARLY WED TOWARD THE U.S. EAST COAST BY FRI. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z OPERATIONAL MODELS CONFIDENCE: AVERAGE FAIRLY STRONG AGREEMENT CONTINUES TO EXIST WITH THE TIMING/STRENGTH IN HANDLING THE UPPER LOW AND SURFACE REFLECTIONS HAS THEY CROSS THE NORTHERN PLAINS INTO THE GREAT LAKES WED INTO THUR AND THROUGH THE NORTHEAST/MID-ATLANTIC BY FRIDAY. THE 12Z NAM/GFS HAVE TRENDED A BIT FASTER ELONGATING THE UPPER TROUGH FURTHER SOUTH AND EAST THE NAM MORE SO THAN THE GFS. THIS HAS BEEN FOLLOWED BY THE 12 ECMWF...EVEN OUTPACING THE NAM/GFS BY DAY 3 WHEN THE BASE BECOMES EVEN FURTHER NEGATIVE TILT ACROSS SOUTHEAST CANADA. A PREFERENCE TOWARD A 12Z OPERATIONAL MODEL BLEND REMAINS BUT WITH ENOUGH SPREAD AT DAY 3 TO REMAIN AT AVERAGE CONFIDENCE. LOW-MID LEVEL TROUGH AXIS IMPACTING THE SOUTHEAST/FL PENINSULA THROUGH THU POTENTIAL UPPER TROUGH / CLOSED LOW IN THE WRN ATLANTIC BY MID TO LATE WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z NAM/GFS/ECMWF CONFIDENCE: AVERAGE ENSEMBLE MEMBERS FROM THE 06Z GEFS/00Z ECMWF/09Z SREF ENSEMBLE ALONG WITH THEIR OPERATIONAL COMPONENTS HAVE DECREASED IN SPREAD WITH BETTER AGREEMENT IN THE EVOLUTION/DEPTH OF THE TROF AXIS BECOMING A CLOSED LOW BY FRIDAY NORTH OF BAHAMAS. THE 12Z ECMWF CONTINUED ITS TREND TOWARD THE GFS SOLUTION FARTHER UP THE CAROLINA COAST WITH THE SURFACE LOW...AS WELL AS RESOLVING WEAKER VORT CENTER OVER THE WESTERN GULF...IN LINE WITH THE 12Z NAM/GFS. THE 12Z NAM IS A BIT STRONGER WITH THE VORT CENTERS COMPARED TO THE GFS/ECMWF...IN LINE WITH ITS BIAS...HOWEVER HAS GOOD ORIENTATION AND LOCATION TO THE VORT CENTERS OVER THE WESTERN GULF AND NORTH OF THE BAHAMAS TO BE INCLUDED INTO THE BLEND. THE 12Z UKMET REMAINS THE STRONGEST AND MOST CONSOLIDATED WITH VORTICITY ENERGY AS WELL AS DEVELOPING A STRONGER SURFACE LOW NEAR THE CAROLINA COAST BY FRIDAY NIGHT. THE 12Z CMC REMAINS QUITE WEAK WITH LITTLE TO NO TROF DEVELOPMENT. AS SUCH A BLEND OF THE 12Z NAM/GFS/ECMWF IS PREFERRED WITH CONTINUED BETTER AGREEMENT AND REDUCING SPREAD...CONFIDENCE IS INCREASED TO AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA