243
FXUS10 KWNH 310723
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
323 AM EDT SAT AUG 31 2019
VALID AUG 31/0000 UTC THRU SEP 03/1200 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: NON-NAM, NON-CMC BLEND
CONFIDENCE: ABOVE AVERAGE
07Z UPDATE: THE PRIMARY DISCREPANCIES IN THE SYNOPTIC PATTERN
INVOLVE A SHORTWAVE MOVING INTO THE PACIFIC NW ON DAY 2 AND THEN
INTO THE NORTHERN PLAINS MONDAY. THE NAM AND CMC ARE NOW BOTH FAST
OUTLIERS RACING THIS FEATURE EASTWARD, FAR OUTPACING THE REMAINING
GLOBAL SUITE. OTHERWISE, THE MODELS ARE WELL CLUSTERED ACROSS THE
CONUS.
PREVIOUS DISCUSSION:
THE GLOBAL SUITE REMAINS IN GOOD AGREEMENT IN A
WESTERN-RIDGE/EASTERN-TROUGH SETUP THROUGH THE NEXT 3 DAYS. WHILE
SMALL SCALE PERTURBATIONS IN THE FLOW WILL IMPACT QPF, THERE IS
GENERALLY SMALL SPREAD AMONG THE MAJORITY OF THE MODELS. THE LONE
EXCEPTION IS THE 00Z/31 NAM WHICH BECOMES TOO FAST AND AMPLIFIED
WITH A SHORTWAVE MOVING INTO THE PAC NW ON DAY 2, AND LIFTING INTO
THE NORTHERN PLAINS BY DAY 3. THIS HAS THE EFFECT OF PUSHING THE
ASSOCIATED SURFACE LOW AND COLD FRONT TOO QUICKLY EAST AND TOO
SHARPLY TO THE SOUTH, AND FOR THIS REASON THE NAM IS REMOVED FROM
THE PREFERRED BLEND.
OTHERWISE, THE PREFERENCE THIS CYCLE INCLUDES ALL OTHER AVAILABLE
GUIDANCE, ACCOUNTING FOR THE TYPICAL BIASES.
..HURRICANE DORIAN
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PLEASE REFER TO THE OFFICIAL NATIONAL HURRICANE CENTER FORECAST
TRACK
INITIALLY, THE GFS/ECMWF ARE THE BEST PROXY FOR THE NHC TRACK FOR
HURRICANE DORIAN. HOWEVER, BY DAY 3, THE GFS BECOMES TOO FAST
WHILE THE UKMET/ECMWF SLOW ACROSS THE BAHAMAS TO BECOME MORE
ALIGNED WITH 03Z ADVISORY POSITIONS. FOR THIS REASON A
GFS/ECMWF/UKMET BLEND IS PREFERRED TO MAINTAIN INTEGRITY OF THE
NHC TRACK, BUT NOTE MORE WEIGHT ON THE GFS THE FIRST 48 HOURS,
TRENDING TOWARDS HIGHER UKMET 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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