352
FXUS10 KWNH 271856
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
255 PM EDT MON APR 27 2020
VALID APR 27/1200 UTC THRU MAY 01/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING LATEST PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..DEEP TROUGH/LOW CENTER EXITING THE NORTHEAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS GRADUALLY TAKE THE DEEP UPPER TROUGH AND ASSOCIATED
CLOSED LOW IMPACTING THE NORTHEAST GRADUALLY AWAY FROM THE REGION
THROUGH TUESDAY. THE GUIDANCE SHOWS RATHER MINIMAL MODEL MASS
FIELD SPREAD AS THE SYSTEM EXITS AWAY, AND SO A GENERAL MODEL
BLEND WILL BE PREFERRED.
..NORTHERN STREAM TROUGH AMPLIFYING OVER THE MIDWEST
..SYSTEM ADVANCING INTO THE EASTERN U.S. BY THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z UKMET/ECMWF AND 12Z GEFS MEAN
CONFIDENCE: AVERAGE
A NORTHERN STREAM SHORTWAVE TROUGH CLIPPING THE PACIFIC NORTHWEST
AND SOUTHERN BRITISH COLUMBIA TODAY IS EXPECTED TO AMPLIFY
SOUTHEASTWARD DOWN ACROSS THE MIDWEST BY WEDNESDAY IN RESPONSE TO
A DEEP LAYER RIDGE DEVELOPING OVER THE WESTERN U.S. AND SOUTHWEST
CANADA GOING THROUGH THE MIDDLE OF THE WEEK. THE GUIDANCE SHOWS A
STRONG CLOSED LOW EVOLVING OVER THE MIDWEST WHICH WILL FOCUS ON
THE OH VALLEY AND WESTERN GREAT LAKES REGION BY THURSDAY AS A DEEP
LAYER TROUGH ENVELOPS MUCH OF THE EASTERN U.S. BY THAT TIME
PERIOD. ALL OF THE MODEL SHOW REASONABLY GOOD AGREEMENT WITH THE
HEIGHT FALL EVOLUTION AND SURFACE CYCLOGENESIS GOING THROUGH
WEDNESDAY. BY THURSDAY, THERE IS SOME SPATIAL SPREAD WITH THE
SURFACE LOW EVOLUTION AS THE 12Z NAM/GFS SOLUTIONS TAKES THE
SURFACE LOW/ENERGY A LITTLE MORE QUICKLY NORTH ACROSS THE GREAT
LAKES, WITH THE 00Z NON-NCEP SOLUTIONS TENDING TO KEEP LOW
PRESSURE CONFINED MORE TO THE OH VALLEY, AND WITH A BIT BETTER
DEFINED TRIPLE-POINT LOW OVER THE MID-ATLANTIC STATES AT THE END
OF THE PERIOD GIVEN PLACEMENT OF STRONGER HEIGHT FALLS FOCUSING
STILL A TAD FARTHER SOUTH.
HOWEVER, THE 12Z NON-NCEP SOLUTIONS (NOTABLY THE UKMET AND ECMWF)
DID TREND TO TREND JUST A TAD TOWARD THE NAM/GFS CAMP. LIKE ITS
PREDECESSOR, THE 12Z CMC STILL APPEARS TO BE A BIT TOO WEAK WITH
ITS SURFACE LOW REFLECTION, BUT THE CMC ALSO HAS ITS ENERGY STILL
ON THE SOUTH SIDE OF THE GUIDANCE AT THE END OF THE PERIOD. THE
12Z CMCE AND 00Z ECENS MEANS STILL FAVOR THE FARTHER SOUTH
SOLUTION AS WELL. THE 12Z GEFS MEAN THOUGH IS VERY CLOSE TO THE
NEW ECMWF AT THIS POINT, WITH THE GFS STILL A TAD NORTH OF THIS
CAMP. BASED ON THE LATEST TRENDS AND CLUSTERING, A BLEND OF THE
12Z UKMET/ECMWF AND 12Z GEFS MEAN WILL BE PREFERRED. THIS BEST
APPROXIMATES THE MODEL CONSENSUS WITH THE NAM/GFS SOLUTIONS STILL
OVERALL ON THE NORTH SIDE OF THE GUIDANCE AND THE CMC ON THE SOUTH
SIDE.
..WEAK SHORTWAVE CLIPPING THE NORTHWEST ON WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
A MODEST AND RATHER PROGRESSIVE SHORTWAVE TROUGH WILL COME IN OFF
THE PACIFIC OCEAN AND CLIP AREAS OF THE PACIFIC NORTHWEST AND
SOUTHERN BRITISH COLUMBIA BY LATE WEDNESDAY. A WEAK AREA OF LOW
PRESSURE AN ATTENDANT FRONT IS EXPECTED TO ACCOMPANY THIS ENERGY.
THE 00Z ECMWF WAS PERHAPS A TAD SLOWER THAN THE MODEL CONSENSUS,
BUT THE MODEL DIFFERENCES ARE QUITE MODEST, SO A GENERAL MODEL
BLEND WILL BE PREFERRED WITH THIS SYSTEM.
..SHORTWAVE MOVING INTO THE WEST ON THURSDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-GFS BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS BRING ANOTHER SHORTWAVE TROUGH IN OFF THE PACIFIC OCEAN
ON THURSDAY AND IN ACROSS PORTIONS OF THE WEST. THE GUIDANCE
REFLECTS A RELATIVELY LOW-AMPLITUDE TO THIS SYSTEM AT LEAST
THROUGH THIS PERIOD, BUT THE GFS IS TAD STRONGER THAN THE NAM AND
ALSO THE NON-NCEP MODELS AT THIS POINT. THE LATEST GEFS/ECENS
MEANS ARE NOT AS ROBUST AS THE DETERMINISTIC GFS, AND SO WILL
SUGGEST LEANING AWAY FROM THE RELATIVELY DEEPER GFS AT THIS POINT.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
ORRISON
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