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FXUS10 KWNH 161630
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1229 PM EDT THU JUL 16 2020
VALID JUL 16/1200 UTC THRU JUL 20/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION INCLUDING PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...LONG WAVE TROUGH CROSSING THE NORTH CENTRAL US INTO EASTERN
CANADA THROUGH FRI WITH AN ACCOMPANYING SURFACE COLD FRONT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE CONSENSUS WITH BOTH THE MID LEVEL
TROUGH AND ITS ATTENDANT SURFACE COLD FRONT CROSSING THE NORTHEAST
FRI (THOUGH THE 12Z GFS COULD BE A BIT FAST WITH THE FRONTAL
PASSAGE ON THE EAST COAST). BASED ON THE GOOD CLUSTERING IN THE
MID LEVEL AND AT THE SURFACE, A GENERAL MODEL BLEND IS PREFERRED
WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE.
..CUT OFF LOW WEST OF CALIFORNIA THROUGH FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
BOTH THE 12Z NAM/GFS ARE CLUSTERED WELL WITH THE CONSENSUS TAKING
THE MID LEVEL SYSTEM JUST OFF THE SOUTHERN CA COAST TODAY AND
TRACKING IT WESTWARD INTO THE PACIFIC UNDER THE BROAD MID LEVEL
RIDGE EXTENDING ACROSS MUCH OF THE SOUTHERN PORTIONS OF THE US.
GIVEN THE TIGHT CLUSTERING, A GENERAL MODEL BLEND IS PREFERRED
WITH ABOVE AVERAGE FORECAST CONFIDENCE.
...LONG WAVE TROUGH CROSSING THE PACIFIC NORTHWEST TODAY, MOVING
INTO SOUTH CENTRAL CANADA BY SAT, THEN CLIPPING THE NORTHERN
PLAINS INTO UPPER GREAT LAKES BY SUN...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-12Z NAM BLEND
CONFIDENCE: AVERAGE
THE 12Z NAM/GFS ARE CLOSE TO THE MODEL CONSENSUS TAKING THE LONG
WAVE TROUGH FROM THE PACIFIC NORTHWEST AND BRITISH COLUMBIA AND
CLOSING OFF A MID LEVEL SYSTEM OVER MANITOBA NEAR 19/00Z. AFTER
THAT TIME, THE 12Z NAM BECOMES DEEPER AND SLOWER WITH THE SHORT
WAVE ENERGY SOUTH OF THE CLOSED LOW ACROSS THE NORTHERN PLAINS
INTO THE UPPER GREAT LAKES, PARTICULARLY DURING DAY 3. THE
DEEPER/SLOWER SHORT WAVE ENERGY ALLOWS THE 12Z NAM TO DEVELOP A
DEEPER SURFACE LOW ON A FRONT EXTENDING ACROSS THE AREA (SOMETHING
THE NAM DOES OFTEN IN THIS SITUATION). BASED ON THIS, THE 12Z NAM
WAS NOT INCLUDED IN THE MODEL PREFERENCE.
DURING DAY 3, BECAUSE OF THE FAST MID LEVEL FLOW SOUTH OF THE
CLOSED MID LEVEL LOW, THE TIMING OF THE SHORT WAVES BECOME MORE
NEBULOUS WITH TIME. WHILE A GENERAL MODEL BLEND SHOULD SUFFICE,
PERHAPS USING THE 00Z GEFS MEAN AND 00Z ECMWF ENSEMBLE MEAN COULD
DAMPEN SOME OF THE DIFFERENCES IN THE TIMING IN THE FAST FLOW.
BECAUSE OF THE SUBTLE DIFFERENCES IN THE SHORT WAVE TIMING, THE
FORECAST CONFIDENCE IS ONLY AVERAGE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
HAYES
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