244
FXUS10 KWNH 031845
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
244 PM EDT SUN MAY 3 2020
VALID MAY 3/1200 UTC THRU MAY 7/0000 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION INCLUDING INITIAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
SHORTWAVE AND SURFACE LOW TRACKING FROM GREAT LAKES TO THE
NORTHEAST THROUGH MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: HIGH
SHORTWAVE TROUGH WITH COLD FRONT CURRENTLY CROSSING THE
APPALACHIANS AND MID-ATLANTIC WILL CONTINUE SLOWLY TRACKING EAST
WITH PARENT SURFACE LOW EXITING EASTERN NEW ENGLAND BY MONDAY
AFTERNOON. ONLY MINOR TIMING DIFFERENCES EXIST WITH THIS SYSTEM,
AND ALTHOUGH THE 12Z GFS IS SLIGHTLY FASTER AND THE 12Z CMC A
LITTLE WEAKER ONCE EMERGING OFFSHORE NEAR NEW ENGLAND, THE
DIFFERENCES ARE SMALL ENOUGH THAT A GENERAL MODEL BLEND CAN BE
USED FOR THIS SYSTEM FROM THE GREAT LAKES, NORTHEAST AND
CENTRAL/SOUTHERN APPALACHIANS.
MID-LEVEL SHORTWAVE OVER THE NORTHERN ROCKIES THIS AFTERNOON,
EVENTUALLY REACHING THE OHIO VALLEY BY WEDNESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/CMC BLEND
CONFIDENCE: MODERATE
A COMPLEX EVOLUTION WILL TAKE PLACE AS A SHORTWAVE TROUGH OVER
INTERIOR PORTIONS OF THE NORTHWEST TRACKS SOUTHEASTWARD IN
CONJUNCTION WITH A CLOSED LOW CROSSING SOUTHERN
ALBERTA/SASKATCHEWAN ON MONDAY. AT THE SAME TIME, A WEAKER
MID-LEVEL SHORTWAVE IS EXPECTED TO TRACK EASTWARD ACROSS THE
INTERMOUNTAIN WEST, REACHING THE UPPER MIDWEST BY MONDAY NIGHT,
WITH SOME PHASING BETWEEN THESE TWO DISTURBANCES. AT THE SURFACE,
CYCLOGENESIS IS EXPECTED TO DEVELOP OVER THE MID-SOUTH BY MONDAY
NIGHT ALONG A FRONTAL BOUNDARY, AND THEN REACH THE EAST COAST BY
WEDNESDAY MORNING AS MILLER-B CYCLOGENESIS TAKES PLACE EAST OF
NORTH CAROLINA. THE GFS TRENDED A LITTLE MORE AMPLIFIED ACROSS
THE OHIO VALLEY AND THE MID-SOUTH COMPARED TO ITS 6Z RUN, AND THE
12Z CMC IS SLIGHTLY SUPPRESSED WITH ITS SURFACE LOW TRACK. THE
12Z UKMET IS NOW THE MOST POTENT WITH THE UPPER LEVEL SHORTWAVE
AND SLOWER TO ERODE THE PRIMARY SURFACE LOW OVER THE CENTRAL
APPALACHIANS BY THE END OF THE FORECAST PERIOD. THERE HAS ALSO
BEEN A TREND IN THE NON-NCEP GUIDANCE TODAY FOR A MORE AMPLIFIED
TROUGH OVER THE EASTERN U.S. IN COMPARISON TO THEIR 00Z RUNS.
THERE IS ENOUGH SYNOPTIC SCALE AGREEMENT AMONG THE ECMWF/GFS/CMC
TO MERIT A BLEND OF THOSE MODELS.
PAIR OF SHORTWAVE TROUGHS AFFECTING THE PACIFIC NORTHWEST THROUGH
TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/12Z GFS/00Z ECENS BLEND
CONFIDENCE: MODERATE
THE FIRST OF TWO SHORTWAVE TROUGHS TO PIVOT AROUND THE BROAD UPPER
LEVEL GYRE OVER THE GULF OF ALASKA WILL CLIP THE PACIFIC NORTHWEST
MONDAY NIGHT, WITH THE 00Z UKMET STANDING OUT WITH A STRONGER
SHORTWAVE COMPARED TO THE OTHER MODELS. THE SECOND AND STRONGER
SHORTWAVE THAT FOLLOWS WILL APPROACH THE PACIFIC NORTHWEST ON
TUESDAY/TUESDAY NIGHT WITH AN ACCOMPANYING COLD FRONT AT THE
SURFACE. IN TERMS OF THE LATEST MODEL GUIDANCE, THE CMC IS MORE
PROGRESSIVE WITH THE TROUGH DURING THE DAY 3 PERIOD, AND THE 12Z
GFS TRENDED A LITTLE FASTER COMPARED TO ITS 6Z RUN, ALTHOUGH STILL
A LITTLE SLOWER THAN MOST OF THE GUIDANCE. THE 12Z NAM IS ON THE
STRONGER SIDE OF THE MODEL GUIDANCE, ALONG WITH THE 12Z UKMET BY
WEDNESDAY EVENING ACROSS THE NORTHERN ROCKIES. FOR NOW, A BLEND
OF THE 12Z ECMWF/GFS/00Z ECENS IS CLOSEST TO THE MIDDLE OF THE
ENSEMBLE GUIDANCE AND CLOSEST TO THEIR MEANS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
HAMRICK
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