033
FXUS10 KWNH 040647
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
247 AM EDT MON MAY 04 2020
VALID MAY 04/0000 UTC THRU MAY 07/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SHORTWAVE/CLOSED LOW AND SURFACE CYCLE DEPARTING FROM THE
NORTHEAST THROUGH TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
ONLY MINOR DIFFERENCES REMAIN WITH THIS SYSTEM, SO A GENERAL MODEL
BLEND IS PREFERRED GIVEN THE DIFFERENCES CAN BE AVERAGED OUT WITH
A BLEND. NO SIGNIFICANT DIFFERENCES WERE NOTED WITH THE 00Z
ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS 12Z CYCLES.
...MID-LEVEL SHORTWAVE TRACKING EASTWARD THROUGH THE GREAT PLAINS,
OHIO VALLEY AND EAST COAST THROUGH WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/UKMET/CMC BLEND (LESS WEIGHT ON CMC FOR
WED/WED NIGHT)
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS/ECMWF ARE A LITTLE FASTER THAN THE 00Z UKMET/CMC
REGARDING THE LEADING EDGE OF A 500 MB SHORTWAVE CROSSING THE
MISSISSIPPI RIVER ON TUESDAY. THE 00Z ECMWF SPED UP SLIGHTLY WHILE
THE 00Z UKMET SPED UP MORE TO MATCH THE MODEL CONSENSUS. DESPITE A
GENERALLY STRONGER TREND IN THE GUIDANCE WITH THIS SYSTEM SINCE
YESTERDAY, THE 12Z UKMET IS ON THE EDGE OF THE LATEST ENSEMBLE
MEMBERS AND SHOULD NOT BE USED. THE MIDDLE TO STRONG SIDE OF THE
MODELS FAVORS A NON 00Z NAM BLEND WITH THE 00Z NAM DIFFERING WITH
AN UPSTREAM SECONDARY COLD FRONT MOVING THROUGH THE SOUTHEAST ON
WEDNESDAY.
AS A SURFACE LOW ORGANIZES IN THE WESTERN ATLANTIC ON WEDNESDAY,
SCATTER LOW PLOTS FROM THE ENSEMBLES INDICATE A FAIR AMOUNT OF
SPREAD, BUT THE 00Z CMC IS ON THE WESTERN/SLOWER SIDE OF THE
ENSEMBLES. CLUSTERING AND TRENDS OF LOW PLOTS FAVORS A SOLUTION
CLOSER TO THE 00Z NAM, GFS, ECMWF AND UKMET.
OVERALL A 00Z GFS/ECMWF/UKMET BLEND IS PREFFERED WITH THIS SYSTEM.
INCORPORATION OF THE 00Z CMC IS CONSIDERED OKAY AS WELL PRIOR TO
WEDNESDAY MORNING GIVEN ITS UNFAVORABLE LOW POSITION IN THE
ATLANTIC LATER IN THE PERIOD.
...PAIR OF SHORTWAVE TROUGHS AFFECTING THE PACIFIC NORTHWEST
THROUGH TUESDAY...
..MID-LEVEL SHORTWAVE OVER MONTANA/WYOMING BY THURSDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND
CONFIDENCE: AVERAGE
THE FIRST OF TWO SHORTWAVE TROUGHS TO PIVOT AROUND A BROAD UPPER
LEVEL GYRE OVER THE GULF OF ALASKA WILL CLIP THE PACIFIC NORTHWEST
MONDAY NIGHT. THE 12Z UKMET WAS A LITTLE STRONGER WITH THIS
FEATURE AS ITS FORECAST TO MOVE INLAND ACROSS SOUTHERN BRITISH
COLUMBIA, BUT THE 00Z UKMET ADJUSTED TOWARD THE REMAINING MODEL
CONSENSUS.
AS THE NEXT SHORTWAVE APPROACHES THE PACIFIC NORTHWEST, FORECASTS
INDICATE A RATHER POTENT MID-LEVEL TROUGH TO REACH THE COASTS OF
WASHINGTON AND OREGON TUESDAY NIGHT. MODELS DIFFER WITH THE
DISTRIBUTION OF ENERGY WITHIN THE NORTH-SOUTH AXIS OF VORTICITY,
MOST NOTABLY WITH THE 00Z NAM ON THE SOUTH SIDE OF THE GUIDANCE.
THE SHORTWAVE TROUGH AXIS COMES IN WITH A NEGATIVE TILT ON
WEDNESDAY ACROSS WA/OR/ID AND BY THURSDAY MORNING, MODELS VARY
WITH THE DEPICTION OF THE WAVE. THE 00Z NAM IS FARTHEST NORTH AND
00Z CMC REMAINS FARTHEST SOUTH AFTER NORTHWARD ADJUSTMENTS IN THE
00Z UKMET RELATIVE TO ITS 12Z CYCLE. THE 00Z ECMWF, LIKE THE
UKMET, ADJUSTED A BIT STRONGER WITH THE LOW-MID LEVEL WAVE THROUGH
THURSDAY MORNING. A BLEND OF THE SIMILAR STRENGTH 00Z
GFS/ECMWF/UKMET IS PREFERRED GIVEN ALIGNMENT WITH THE LATEST
ENSEMBLE MEANS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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