318
FXUS10 KWNH 040458
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1258 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 NAM/GFS EVALUATION INCLUDING PRELIMINARY 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.
...MID-LEVEL SHORTWAVE TRACKING EASTWARD THROUGH THE GREAT PLAINS,
OHIO VALLEY AND EAST COAST THROUGH WEDNESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF/12Z CMC BLEND (LESS WEIGHT ON CMC
FOR WED/WED NIGHT)
CONFIDENCE: AVERAGE
THE 00Z NAM/GFS REMAIN FASTER THAN THE 12Z ECMWF/UKMET/CMC
REGARDING THE LEADING EDGE OF A 500 MB SHORTWAVE CROSSING THE
MISSISSIPPI RIVER ON TUESDAY. THE 12Z UKMET IS SLOWEST AND
STRONGER WITH THE SHORTWAVE. 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. THE MIDDLE TO STRONG SIDE
OF THE MODELS FAVORS A BLEND OF THE 00Z GFS, 12Z ECMWF AND 12Z
CMC.
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 12Z CMC AND 12Z UKMET ARE ON THE WESTERN/SLOWER
SIDE OF THE ENSEMBLES. CLUSTERING AND TRENDS OF LOW PLOTS FAVORS A
SOLUTION CLOSER TO THE 00Z NAM, 00Z GFS AND 12Z ECMWF.
OVERALL A 00Z GFS, 12Z ECMWF AND 12Z CMC BLEND IS PREFERRED WITH
THIS SYSTEM, EXCEPT FOR LESS WEIGHT ON THE 12Z CMC FOR WEDNESDAY
INTO THURSDAY GIVEN ITS UNFAVORABLE LOW POSITION IN THE ATLANTIC.
...PAIR OF SHORTWAVE TROUGHS AFFECTING THE PACIFIC NORTHWEST
THROUGH TUESDAY...
..MID-LEVEL SHORTWAVE OVER MONTANA/WYOMING BY THURSDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF/00Z GFS 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 IS A LITTLE STRONGER WITH THIS FEATURE
AS IT MOVES INLAND ACROSS SOUTHERN BRITISH COLUMBIA. OTHERWISE,
THE MODELS ARE IN FAIR AGREEMENT HERE.
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 12Z NON-NCEP CAMP IS A BIT FARTHER NORTH WHEN COMPARED TO THE
LATEST ENSEMBLE MEANS. 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, 12Z UKMET/CMC FARTHEST SOUTH. A BLEND OF THE
STRONGER 00Z GFS AND SOMEWHAT WEAKER 12Z ECMWF IS PREFERRED GIVEN
ALIGNMENT WITH THE LATEST ENSEMBLE MEANS. THIS PREFERENCE CARRIES
THROUGH 12Z/07 AFTER WHICH POINT MODEL DIVERGENCE INCREASES
BETWEEN THE 00Z GFS AND 12Z ECMWF.
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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