817   
FXUS10 KWNH 071648  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1247 PM EDT SAT SEP 07 2019  
  
VALID SEP 07/1200 UTC THRU SEP 11/0000 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 12Z NAM/GFS BLEND...PLAINS/MIDWEST  
            GENERAL MODEL BLEND...REMAINDER OF CONUS  
CONFIDENCE: AVERAGE  
  
THE MODELS ARE IN GOOD AGREEMENT WITH THE LARGE SCALE SYNOPTIC  
EVOLUTION ACROSS THE CONUS OVER THE NEXT FEW DAYS. THIS WILL  
INVOLVE THE AMPLIFICATION OF A DEEP TROUGH ACROSS THE WEST BY  
TUESDAY, AND A RATHER STRONG DEEP LAYER RIDGE OVER THE SOUTHEAST.  
MEANWHILE, THE DEEP TROUGHING OVER THE NORTHEAST OVER THE NEXT 1  
TO 2 DAYS WHICH CAPTURES THE RAPIDLY DEPARTING HURRICANE DORIAN  
APPROACHING NOVA SCOTIA WILL LIFT NORTHEAST ACROSS SOUTHEAST  
CANADA WITH TIME AND ALLOW FOR STEADY HEIGHT RISES IN ITS WAKE.  
  
AS THE LARGER SCALE FLOW BECOMES MORE AMPLIFIED WITH TIME, THE  
GUIDANCE TAKES THE INITIAL SHORTWAVE TROUGH EJECTING OUT ACROSS  
THE NORTHERN PLAINS TODAY OFF TO THE EAST AND ACROSS THE UPPER  
MIDWEST THROUGH SUNDAY WHILE GRADUALLY DAMPENING IT OUT. THE MODEL  
DIFFERENCES WITH THIS SYSTEM ARE MODEST WITH THE 12Z NAM AND 12Z  
GFS JUST A TAD MORE AMPLIFIED AND A LITTLE SLOWER THAN THE 00Z  
NON-NCEP CAMP OF GUIDANCE INCLUDING THE UKMET, CMC AND ECMWF.  
MEANWHILE, A NEGATIVELY TILTED TROUGH CROSSING THE WEST COAST  
LATER TODAY WILL ADVANCE INTO THE INTERMOUNTAIN REGION ON SUNDAY.  
ON MONDAY, THIS SYSTEM WILL PROGRESSIVELY CROSS THE CENTRAL AND  
NORTHERN PLAINS AND BEGIN TO DAMPEN OUT AS IT ENCOUNTERS  
INCREASINGLY CONFLUENT MID/UPPER-LEVEL FLOW DOWNSTREAM. THERE ARE  
SOME NOTABLE TIMING DIFFERENCES WITH THIS FEATURE AS THE 12Z NAM  
AND 12Z GFS HAVE BOTH TRENDED A BIT MORE PROGRESSIVE WITH THE  
ENERGY AS IT EJECTS OUT ACROSS THE PLAINS, AND ARE BOTH FASTER  
THAN THE 00Z NON-NCEP SUITE OF GUIDANCE. THIS DRIVES THE NAM AND  
GFS TO HAVE A MORE PROGRESSIVE SURFACE LOW EVOLUTION, AND HAS A  
DIRECT IMPACT ON THE MODEL QPF, ESPECIALLY BY LATE MONDAY INTO  
TUESDAY ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION.  
  
THE PREFERENCE WILL BE TO LEAN TOWARD A BLEND OF THE NAM AND GFS  
WITH ALL OF THE SHORTWAVE ENERGY IMPACTING THE CENTRAL/NORTHERN  
PLAINS AND MIDWEST THROUGH THE PERIOD. HOWEVER, A GENERAL MODEL  
BLEND SHOULD SUFFICE ELSEWHERE GIVEN STRONG MULTI-MODEL  
CLUSTERING/AGREEMENT.  
  
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
ORRISON  
  
  
 
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