875
FXUS10 KWNH 020442
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1142 PM EST SUN DEC 01 2019
VALID DEC 02/0000 UTC THRU DEC 05/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP CLOSED LOW IMPACTING THE MID-ATLANTIC/NEW ENGLAND
..SURFACE LOW PRESSURE LIFTING OFFSHORE THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z NAM/HREF...THROUGH 36 HOURS
BLEND OF THE 00Z NAM/GFS AND 12Z ECMWF...AFTER 36 HOURS
CONFIDENCE: ABOVE AVERAGE
DIFFERENCES WITH THIS SYSTEM ARE RELATIVELY MINOR ALOFT, REGARDING
THE 500/700 MB CLOSED LOW POSITIONS AND STRENGTH. HOWEVER, THE 12Z
UKMET IS A BIT SLOWER AND FARTHER WEST WITH ITS CLOSED LOW AND
SURFACE REFLECTION AS THE SYSTEM LIFTS UP OFFSHORE NEW ENGLAND AND
THROUGH THE GULF OF MAINE ON TUESDAY. THE 00Z NAM AND THE HIRES
HREF GUIDANCE PER THE 00Z ARW/ARW2 AND 00Z NMMB ARE RATHER WELL
CLUSTERED WITH THE EVOLUTION OF THE SYSTEM, AND COLLECTIVELY ARE
TAKING LOW PRESSURE JUST A TAD EAST OF THE GLOBAL MODEL CONSENSUS
WHICH IS BEST REPRESENTED BY A BLEND OF THE 00Z GFS AND 12Z ECMWF
AT THIS POINT. ACCOUNTING FOR A SUBTLE EASTWARD SHIFT/TREND IN THE
LOW PRESSURE TRACK WITH THE LATEST HIRES MODEL SUITE AND THE
NAM/GFS SOLUTIONS, THE LATEST MODEL PREFERENCE WILL BE TOWARD A
NAM/HREF BLEND THROUGH ABOUT 36 HOURS, AND THEN A BLEND OF THE 00Z
NAM/GFS AND 12Z ECMWF THEREAFTER.
..UPPER LOW OFFSHORE THE WEST COAST THROUGH TUESDAY
..ENERGY THEN CROSSING THE SOUTHWEST ON WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 36 HOURS
BLEND OF THE 00Z NAM/GFS AND 12Z CMC...AFTER 36 HOURS
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THERE IS RATHER GOOD AGREEMENT WITH THE EVOLUTION OF THE UPPER LOW
OFFSHORE THE WEST COAST THROUGH ABOUT 36 HOURS, BUT THEREAFTER THE
12Z UKMET TENDS TO BE A LITTLE SLOWER AND SOUTH OF THE MULTI-MODEL
CONSENSUS. MEANWHILE, THERE IS A PERIOD BETWEEN ABOUT 48 HOURS AND
72 HOURS WHEN THE 12Z ECMWF IS ON THE NORTH SIDE OF THE GUIDANCE,
ALTHOUGH AS THE SYSTEM THEN EJECTS ACROSS THE SOUTHWEST LATER
WEDNESDAY, THE ECMWF COMES BACK INTO BETTER AGREEMENT WITH THE
GUIDANCE OUTSIDE OF THE UKMET. THE 00Z NAM, 00Z GFS AND 12Z CMC
ARE CLUSTERED TOGETHER RATHER WELL THROUGH THE PERIOD, AND ARE
SUPPORTED BY THE 18Z GEFS MEAN, AND SO A BLEND OF THESE SOLUTIONS
WILL BE FAVORED AFTER 36 HOURS, WITH A GENERAL MODEL BLEND PRIOR
TO THIS.
..SHORTWAVE CROSSING THE NORTHERN PLAINS/UPPER MIDWEST MONDAY
..AMPLIFYING ACROSS THE OH VALLEY/NORTHEAST TUESDAY/WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 48 HOURS
BLEND OF THE 00Z NAM/GFS AND 12Z ECMWF...AFTER 48 HOURS
CONFIDENCE: ABOVE AVERAGE
THE MODELS BRING A NORTHERN STREAM SHORTWAVE SOUTHEAST ACROSS
PORTIONS OF THE NORTHERN PLAINS AND UPPER MIDWEST ON MONDAY AND
THEN DROP IT DOWN ACROSS THE OH VALLEY AND NORTHEAST THROUGH
TUESDAY AND WEDNESDAY. THE GUIDANCE IS IN GOOD AGREEMENT WITH THIS
EVOLUTION THROUGH 48 HOURS, BUT THEREAFTER THE 12Z CMC AND TO SOME
EXTENT THE 12Z UKMET EDGE STRONGER THAN THE REMAINING GUIDANCE AS
THE TROUGH AMPLIFIES IN ACROSS THE NORTHEAST. THE UKMET ALSO
BECOMES A LITTLE SLOWER THAN THE OTHER MODELS WITH ITS TIMING. THE
BETTER MODEL CLUSTERING AND ENSEMBLE SUPPORT RESIDES MORE WITH THE
00Z NAM/GFS AND 12Z ECMWF, AND SO A BLEND OF THESE SOLUTIONS WILL
BE PREFERRED AFTER 48 HOURS. A GENERAL MODEL BLEND WILL BE
PREFERRED PRIOR TO THIS.
..WEAK SHORTWAVE/LOW CLIPPING THE NORTHERN PLAINS WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 00Z GFS/12Z UKMET AND 12Z ECMWF
CONFIDENCE: BELOW AVERAGE
THE MODELS SUPPORT A WEAK SHORTWAVE AND ASSOCIATED SURFACE
LOW/FRONT CLIPPING THE NORTHERN PLAINS LATE WEDNESDAY AND THROUGH
EARLY THURSDAY. THERE IS CONSIDERABLE MODEL SPREAD WITH THIS
FEATURE AS THE 00Z NAM IS A FASTER AND YET DEEPER OUTLIER COMPARED
TO THE GLOBAL MODELS. MEANWHILE, THE 12Z CMC GLOBAL IS THE SLOWEST
SOLUTION. THE 00Z GFS, 12Z UKMET AND 12Z ECMWF ALL SPLIT THE
DIFFERENCE WITH TIMING, BUT AT THE SURFACE THERE IS LATITUDINAL
SPREAD WITH THE SURFACE LOW. THE ECMWF IS NORTH OF THE UKMET AND
GFS, WITH THE 12Z ECENS MEAN SUPPORTING THE ECMWF. HOWEVER, THE
18Z GEFS MEAN LOOKS NOTHING LIKE THE GFS/UKMET OR ECMWF SOLUTIONS
AND ACTUALLY FAVORS A SOLUTION CLOSER TO THE NAM. CONFIDENCE IS
BELOW AVERAGE, BUT FOR NOW THE BEST CLUSTERING OF SOLUTIONS WOULD
FAVOR A BLEND OF THE GFS, UKMET AND ECMWF GIVEN CLOSE PROXIMITY OF
THE ECENS MEAN, SO A BLEND OF THESE SOLUTIONS WILL BE PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
ORRISON
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