525
FXUS10 KWNH 220445
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1244 AM EDT WED APR 22 2020
VALID APR 22/0000 UTC THRU APR 25/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP TROUGH/CLOSED LOW INITIALLY OVER THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS ARE IN VERY GOOD AGREEMENT WITH THE DETAILS OF THE DEEP
TROUGH AND CLOSED LOW IMPACTING THE NORTHEAST THROUGH WEDNESDAY.
THE SYSTEM SHOULD EXIT UP ACROSS SOUTHEAST CANADA BY THURSDAY. A
GENERAL MODEL BLEND WILL BE PREFERRED.
...SOUTHERN STREAM TROUGH CROSSING THE SOUTHERN PLAINS/LOWER MS
VALLEY THROUGH EARLY THURSDAY...
...ASSOCIATED ENERGY AND SURFACE LOW CROSSING THE OH VALLEY AND
MID-ATLANTIC BY FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z UKMET/ECMWF AND 18Z GEFS/12Z ECENS MEAN BLEND
CONFIDENCE: AVERAGE
THE MODELS TAKE THE SOUTHERN STREAM MID-LEVEL TROUGH OVER THE
SOUTHWEST OFF TO THE EAST OVER THE NEXT COUPLE OF DAYS, WITH THE
ENERGY CROSSING THE SOUTHERN PLAINS ON WEDNESDAY AND REACHING THE
LOWER MS VALLEY BY EARLY THURSDAY. THIS ENERGY ALONG WITH A
DEEPENING SURFACE LOW CENTER WILL THEN ADVANCE NORTHEAST AND CROSS
THE OH VALLEY AND MID-ATLANTIC REGION BY FRIDAY AS AN ATTENDANT
COLD FRONT SWEEPS ACROSS THE SOUTH. THE SYSTEM WILL EXIT OFFSHORE
BY FRIDAY NIGHT. THE 00Z NAM/GFS SOLUTIONS ARE OVERALL STILL A TAD
FASTER THAN THE NON-NCEP GUIDANCE, WITH THE NAM THE FASTEST WITH
THE TROUGH AND SURFACE LOW. CONSIDERING THE AMPLITUDE OF THE
EJECTING SHORTWAVE, THE NAM APPEARS TOO WEAK WITH ITS SURFACE
REFLECTION. THE GFS FOR ITS PART MAY PERHAPS BE EPISODICALLY BE A
TAD TOO FAST, BUT THE BIGGER CONCERN MAY TEND TO BE WITH THE
OVERALL LATITUDE OF ITS SURFACE LOW TRACK INVOLVING THE OH
VALLEY/MID-ATLANTIC, WHICH IS A LITTLE NORTH OF THE GENERALLY WELL
CLUSTERED 12Z NON-NCEP SOLUTIONS. IT SHOULD BE NOTED THOUGH THAT
THE 12Z CMC APPEARS TO BE A TAD TOO WEAK WITH ITS SURFACE LOW.
REGARDING TIMING AND DEPTH OF THE SYSTEM, THE 12Z UKMET AND 12Z
ECMWF TEND TO HAVE BETTER ENSEMBLE SUPPORT (I.E. 18Z GEFS/12Z
ECENS MEANS). SO, WILL FAVOR A BLEND OF THE UKMET/ECMWF SOLUTIONS
AND ALONG WITH THE ENSEMBLE MEANS FOR THE TIME BEING.
..INITIAL SHORTWAVE/LOW CENTER ACROSS THE NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS BRING A NORTHERN STREAM SHORTWAVE AND ASSOCIATED LOW
CENTER DOWN FROM CANADA AND ACROSS THE NORTHERN PLAINS ON
WEDNESDAY WHICH IS EXPECTED TO DAMPEN OUT OVER THE MIDWEST
WEDNESDAY NIGHT AS THE STRONGER SOUTHERN STREAM SYSTEM EVOLVES
ACROSS THE SOUTHERN PLAINS AND LOWER MS VALLEY. A GENERAL MODEL
BLEND WILL BE PREFERRED WITH THIS SYSTEM GIVEN VERY MODEST MODEL
MASS FIELD SPREAD.
..SHORTWAVE TROUGH DIGGING ACROSS THE INTERMOUNTAIN WEST
..ENERGY AMPLIFYING INTO THE LOWER MS VALLEY BY SATURDAY
..ASSOCIATED DEEPENING SURFACE LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND...THROUGH 60 HOURS
12Z CMC/ECMWF AND 18Z GEFS/12Z ECENS MEAN
BLEND...AFTER 60 HOURS
CONFIDENCE: AVERAGE
THE MODELS BRING YET ANOTHER SHORTWAVE DOWN ACROSS THE
INTERMOUNTAIN WEST WHICH IS THEN FORECAST TO AMPLIFY ACROSS THE
SOUTHERN PLAINS ON FRIDAY AND CROSS THE LOWER MS VALLEY BY EARLY
SATURDAY. THE MODELS, ESPECIALLY THE NON-NCEP MODELS, SHOW THE
TROUGH BECOMING NEGATIVELY TILTED BY EARLY SATURDAY AND THIS WILL
DRIVE ANOTHER DEEPENING SURFACE LOW CENTER. THE 00Z NAM BECOMES A
WEAKER OUTLIER SOLUTION AT THE SURFACE AND ALOFT WITH THE SYSTEM.
THE 00Z GFS APPEARS TO BE A BIT TOO PROGRESSIVE BY FRIDAY/SATURDAY
AND PROBABLY TAKES ITS ENERGY A TAD TOO FAR NORTH, INCLUDING ITS
SURFACE LOW. THE SLOWER NON-NCEP SOLUTIONS ARE PREFERRED AS THEY
HAVE BETTER ENSEMBLE SUPPORT FROM THE 18Z GEFS AND 12Z ECENS MEANS
YET AGAIN. THE UKMET THOUGH DOES APPEAR TO BE A BIT TOO SLOW BY
THE END OF THE PERIOD AS IT ENDS UP SLOWER THAN THE ENSEMBLE
GUIDANCE. SO, WILL PREFER A BLEND OF THE 12Z CMC/ECMWF SOLUTIONS
AND THE 18Z GEFS/12Z ECENS MEANS WITH THIS NEXT SYSTEM, ESPECIALLY
AFTER ABOUT 60 HOURS. PRIOR TO THIS TIME PERIOD, THE MODEL MASS
FIELD SPREAD IS MINIMAL, SO A GENERAL MODEL BLEND CAN BE PREFERRED
PRIOR TO 60 HOURS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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