558   
FXUS10 KWNH 010747  
PMDHMD  
  
MODEL DIAGNOSTIC DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
346 AM EDT SUN SEP 01 2019  
  
VALID SEP 01/0000 UTC THRU SEP 04/1200 UTC  
  
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR  
INGEST...  
  
00Z FINAL MODEL EVALUATION, CONFIDENCE, AND PREFERENCES  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
   
..OVERALL PATTERN ACROSS THE CONUS  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PREFERENCE: 00Z GEFS/00Z ECMWF/00Z NAM  
CONFIDENCE: AVERAGE  
  
07Z UPDATE: LITTLE DIFFERENCES NOTED IN THE 00Z NON-NCEP SUITE.  
THERE REMAINS ABOVE NORMAL SPREAD IN THE NORTHWEST LATE ON DAY 2  
INTO DAY 3 WHICH CAUSES SOME LOWERED CONFIDENCE, BUT THE  
PREFERENCES REMAIN THE SAME.  
  
PREVIOUS DISCUSSION:  
THE OVERALL SYNOPTIC PATTERN WILL PERSIST WITH A RIDGE IN THE WEST  
AND A TROUGH IN THE EAST. WHILE THE GUIDANCE IS WELL CLUSTERED IN  
THE BROAD EVOLUTION, THERE ARE SIGNIFICANT DIFFERENCES THAT ARISE  
IN DAY 2, AND EVEN MORESO ON DAY 3, ACROSS THE NW AND NORTHERN  
TIER. A SHORTWAVE MOVING INTO THE PACNW WILL EJECT EASTWARD MONDAY  
INTO TUESDAY, WITH SHORTWAVE RIDGING DEVELOPING QUICKLY IN ITS  
WAKE. THE CMC IS VERY QUICK TO PUSH THIS ENERGY EASTWARD,  
OUTPACING THE GLOBAL CONSENSUS CONSIDERABLY. THE GFS IS ON THE  
OTHER SIDE OF THE SPECTRUM, WITH THE SHORTWAVE MOVING SO SLOWLY  
THAT IT HANGS BACK AND CUTS OFF INTO A MID-LEVEL LOW WHERE THE  
REMAINING GUIDANCE HAS UPSTREAM RIDGING. THIS SEEMS UNLIKELY AS  
THE FLOW ACROSS THE NORTHERN TIER IS MODESTLY FAST EMBEDDED WITHIN  
A 90 KT UPPER JET. THE UKMET IS USABLE, BUT ITS HEIGHTS ARE A FEW  
DM HIGHER AS IT MAINTAINS THE STRENGTH OF THE RIDGE MORE STRONGLY  
THAN THE REMAINING GUIDANCE. THE NEW NAM LOOKS VERY MUCH LIKE THE  
ECMWF AND THE 18Z GEFS MEAN, BRINGING SOME CONSISTENCY TO  
OTHERWISE MESSY 60-84 HOUR MASS FIELDS.  
  
   
..HURRICANE DORIAN  
  
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  
PLEASE REFER TO THE OFFICIAL NATIONAL HURRICANE CENTER FORECAST  
TRACK  
  
THE ECMWF/UKMET/GFS ARE VERY TIGHTLY CLUSTERED TO THE 03Z NHC  
TRACK INTO DAY 2. AFTER 48 HOURS, THE BEST PROXY BLEND BEGINS TO  
DIVERGE SUCH THAT THE GFS/UKMET ARE CLOSEST TO THE NHC TRACK, AND  
LATE INTO DAY 3 THE GFS ALONE IS THE BEST PROXY AS THE UKMET IS  
TOO FAR WEST, AND THE ECMWF IS TOO SLOW. SO INITIALLY, THE 3  
MODELS CREATE THE CLOSEST BLEND, SLOWLY TRANSITIONING TO THE GFS  
ON DAY 3.  
  
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML  
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML  
  
WEISS  
  
  
 
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