274
FXUS10 KWNH 280638
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
237 AM EDT WED AUG 28 2019
VALID AUG 28/0000 UTC THRU AUG 31/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
EXCEPTION: NON-NAM QPF IN CENTRAL/SOUTHERN PLAINS DAY 3
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
BEST NHC PROXY (ERIN): 18Z GFS OR 00Z GFS/NAM/UKMET/CMC BLEND
(DORIAN)D3: 00Z ECMWF
07Z UPDATE: THE 00Z CMC TRENDED A BIT SLOWER AND FURTHER SOUTH
IN THE WESTERN PORTION OF THE CONUS AND INTO SW CANADA, ENOUGH TO
SUPPORT A GENERAL MODEL BLEND THROUGH THE BULK OF THE CONUS (WITH
THE CONTINUED EXCEPTION OF QPF FROM THE NAM IN THE
CENTRAL/SOUTHERN PLAINS ON DAY 3.
WHILE THE 00Z ECMWF TRENDED SLOWER WITH 06L (ERIN) LIFTING NORTH
AND NOW IS ABOUT THE SAME LATITUDE OF THE OFFICIAL NHC FORECAST,
BUT STILL WELL WEST OF IT. THE REMAINING GUIDANCE, INCLUDING THE
00Z CMC/UKMET/GEFS MEAN MATCH THE 00Z GFS/NAM AND ARE ALONG THE
FORECAST TRACK BUT ABOUT 2-3HRS SLOWER THAN IT. WOULD SUGGEST
UTILIZING A NON-ECMWF PROXY TOWARD THE OFFICIAL FORECAST, OR
REMAIN WITH THE 18Z GFS WHICH REMAINS CLOSEST. AS FOR 05L
(DORIAN), THE 00Z ECMWF SHIFTED NORTH AND IS IN LINE WITH THE
OFFICIAL 03Z NHC FORECAST IN THE 72-84HR TIME PERIOD (31-00Z TO
12Z) AND SO IS CONSIDERED THE BEST PROXY FOR THE FORECAST.
---PRIOR DISCUSSION---
THE SYNOPTIC PATTERN CONTINUES TO BE VERY STRONGLY AGREED UPON
THROUGH THE FIRST 2+ DAYS PARTICULARLY, WITH THE STRONG/DEEP
CLOSED LOW ACROSS ONTARIO. ITS ASSOCIATED FRONTAL ZONE IS, ALSO
WELL AGREED UPON ON DEPTH/TIMING UNTIL THERE IS INTERACTION WITH
THE APPROACH OF TS ERIN. ERIN REMAINS VERY SHEARED WITH LARGE
CONVECTIVE COMPLEX NEAR THE INNER CORE/SURFACE WAVE BUT ALSO HAS A
VERY ELONGATED NORTHERLY SURFACE TROF THAT IS ALREADY SHIFTING
TOWARD THE APPROACHING HEIGHT FALLS. THE 12Z ECMWF IS MOST
AGGRESSIVE NOW, FASTER AND CLOSER TO THE COAST WHILE THE 00Z NAM,
12Z UKMET AND CMC ARE SLOWER BUT MUCH CLOSER IN PLACEMENT. THE
18Z GFS IS VERY CLOSE TO THE OFFICIAL 03Z NHC FORECAST AND IS BEST
TO USE AS NHC BEST PROXY; THE 00Z GFS, SLOWED A FRACTION BUT
MATCHED CLOSEST TO THE CMC, SO IT IS JUST SOUTH OF THE OFFICIAL
FORECAST. SO USE OF THE 18Z GFS IS THE BEST MASS PROXY TO THE
OFFICIAL FORECAST.
BY 60HRS, THE 12Z CMC STARTS TO BREAK DOWN COMPARED TO THE
REMAINING GUIDANCE PARTICULARLY WITH THE APPROACHING
SHORTWAVE/CLOSED LOW NEARING SW CANADA BY 84HRS. THE CMC IS A BIT
FURTHER NORTH OVERALL WITH INCREASED PUMPING OF THE DOWNSTREAM
RIDGE IN THE ROCKIES WHICH STARTS AROUND 60HRS.
AT THE TAIL END OF THE FRONTAL ZONE CROSSING THE NORTHERN
TIER/GREAT LAKES ON THURSDAY AND FRIDAY INTERSECTS WITH THE RETURN
MOISTURE STREAM OVER THE CENTRAL PLAINS, AND MASS FIELDS ARE QUITE
AGREEABLE THROUGH SAT AS WELL, HOWEVER, THE 00Z NAM AND LESSER SO
THE GFS SUGGEST GREATER SOUTHWARD PROPAGATION LIKELY ON STRONGER
LLJ/INFLOW THAN THE UKMET/CMC/ECMWF. THE NAM BECOMES PARTICULARLY
OUT OF PHASE IN THE QPF AXIS TO SUGGEST A LOWER WEIGHTING OR
REMOVAL AT THE END OF DAY 3 IN THIS AREA THOUGH THE REMAINING MASS
FIELDS ARE LESS AFFECTED THAN THE QPF AXIS.
TROPICAL STORM, FORECAST HURRICANE BY DAY 3, DORIAN IS EXPECTED TO
ENTER THE NORTHERN BAHAMAS/SOUTHERN SARGASSO SEA. MODERATELY
SIZABLE SPREAD REMAINS IN PLACEMENT AND STRENGTH. HOWEVER, THE
NAM/CMC ARE MUCH TOO FAR SOUTH TO THE OFFICIAL 03Z FORECAST. THE
GFS/UKMET ARE NORTH OF THE FORECAST TRACK (FAST/SLOW,
RESPECTFULLY) WHILE THE ECMWF IS TIMED IDEALLY IN LONGITUDE BUT A
SHADE SOUTH. AS SUCH, A BLEND OF THE GFS/UKMET AND ECMWF PROVIDES
A GOOD PLACEMENT BLEND, BUT A STRAIGHT BLEND OF THE 3 (IE NOT
RETAINING THE SHAPE/DEPTH/ETC)...SO RE-CENTERING AND BLENDING TO
THE COMMON POINT WOULD BE THE BEST PROXY TO KEEP THE INTEGRITY OF
THE SYSTEM AS A WHOLE.
MODEL TRENDS AT WWW.WPC.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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