573
FXUS10 KWNH 050643
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 AM EDT TUE MAY 05 2020
VALID MAY 05/0000 UTC THRU MAY 08/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL MODEL EVALUATION INCLUDING FINAL PREFERENCES AND
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...SERIES OF MID-LEVEL SHORTWAVES TRACKING ACROSS THE MIDWEST
THROUGH TUESDAY NIGHT, CONSOLIDATING OVER THE MID-ATLANTIC LATE
WEDNESDAY...
...SURFACE LOW DEVELOPMENT OFF OF THE EAST COAST
WEDNESDAY/THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND (LEAST WEIGHT ON 00Z GFS WED - THU
MORNING)
CONFIDENCE: AVERAGE
..07Z UPDATE
THE 00Z ECMWF/UKMET/CMC CONTINUES TO SUPPORT A NON-00Z GFS BLEND
WITH THE 850-500 MB LOW WEDNESDAY INTO THURSDAY OVER THE EASTERN
U.S., BUT ADJUSTMENTS REGARDING THE OFFSHORE SURFACE LOW REPRESENT
A TIGHTER SPREAD. THE 00Z UKMET/CMC ADJUSTED EAST AND THE 00Z
ECMWF TO THE WEST BUT ALSO NORTH. A GENERAL MODEL BLEND CONTINUES
TO BE FAVORED, BUT WITH LITTLE WEIGHT ON THE 00Z GFS FROM
WEDNESDAY TO THURSDAY MORNING.
..PREVIOUS DISCUSSION FOLLOWS
A PAIR OF VORTICITY MAXIMA OVER THE MIDWEST TODAY WILL TRANSITION
EITH EASTWARD EXTENT INTO A STRENGTHENING MID-LEVEL TROUGH BY
WEDNESDAY MORNING. THE 00Z GFS IS STRONGEST WITH THE 850-500 MB
LOW AND ALSO FARTHER NORTH THAN THE CONSENSUS. THIS IS NOTED
ROUGHLY FROM WEDNESDAY TO THURSDAY MORNING.
AS THE TROUGH AXIS MOVES OFFSHORE, SURFACE LOW PRESSURE WILL
ORGANIZE AND TRACK NORTH-NORTHEASTWARD, OFFSHORE OF THE NORTHEAST
COAST. THERE REMAINS SOME NORTH-SOUTH AND EAST-WEST SPREAD IN THE
LATEST ENSEMBLE SCATTER LOT PLOTS WITH THE 12Z UKMET/CMC ON THE
WESTERN SIDE OF THE ENSEMBLE LOWS. THE 18Z GEFS MEAN IS ALSO ON
THE WESTERN SIDE. THEREFORE, A GENERAL MODEL BLEND SHOULD PULL
WEIGHT TOWARD THE MIDDLE OF THE LATEST MODEL SPREAD, EAST OF THE
12Z UKMET/CMC BUT WEST OF THE 12Z ECMWF.
...MID-LEVEL SHORTWAVE MOVING FROM PACIFIC NORTHWEST COAST TUESDAY
NIGHT ACROSS THE NORTHERN ROCKIES WEDNESDAY NIGHT AND THE NORTHERN
PLAINS THURSDAY...
...COLD FRONT DROPPING SOUTHWARD THROUGH THE GREAT PLAINS ON
THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 00Z ECMWF, 00Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..07Z UPDATE
ADJUSTMENTS IN THE 00Z ECMWF/UKMET COMPARED TO THEIR PREVIOUS 12Z
CYCLES CONTINUE TO SUPPORT THE PREVIOUS PREFERENCE. HOWEVER, THE
00Z CMC CONTINUES TO APPEAR TOO FAST WITH THE SHORTWAVE AS IT
APPROACHES THE MISSISSIPPI VALLEY, SIMILAR TO THE 00Z NAM. THE 00Z
UKMET ADJUSTED A LITTLE STRONGER AND SLOWER, WHILE THE 00Z ECMWF
ADJUSTED SLIGHTLY FASTER COMPARED TO ITS 12Z CYCLE WHILE
MAINTAINING A SIMILAR STRENGTH. THEREFORE, WHILE THE 00Z GFS
CONTINUES TO APPEAR TOO STRONG WITH ITS LOW-MID LEVEL SHORTWAVE,
WHEN BLENDED WITH THE 00Z ECMWF/UKMET, A FAVORABLE BLEND IS
REACHED FOR THIS SYSTEM.
..PREVIOUS DISCUSSION FOLLOWS
THERE IS MORE SEPARATION WITH MID-LEVEL VORTICITY MAXIMA EMBEDDED
WITHIN A SHORTWAVE TROUGH ALONG THE WEST COAST WEDNESDAY MORNING
IN THE 00Z NAM THAN THE REMAINING MODEL GUIDANCE. THE 00Z NAM ENDS
UP FASTER WITH THIS LEAD VORTICITY MAX/SHORTWAVE AS IT TRAVERSES
THE WESTERN RIDGE AND AMPLIFIES INTO THE CENTRAL PLAINS.
THE NON-00Z NAM GUIDANCE SHOWS DECENT AGREEMENT BUT THE 12Z CMC
DIFFERS IN THE WAY ITS SHORTWAVE EVOLVES, HOLDING MORE ENERGY BACK
TOWARD THE WEST WHILE THE CONSENSUS IS FOR MORE STRENGTH TOWARD
THE EAST VALID THURSDAY MORNING AT 500 MB. THE 00Z GFS IS BY FAR
THE STRONGEST, DEPICTING A ROBUST MID-LEVEL SHORTWAVE AS IT NEARS
THE MISSISSIPPI VALLEY FRIDAY MORNING. THE GFS'S RESULTANT SURFACE
LOW IS LIKELY TOO STRONG AND LIES ON THE SOUTHERN SIDE OF THE
ENSEMBLE SPREAD. HOWEVER, THE SIMILARLY TIMED 12Z UKMET LOOKS TOO
WEAK/SHEARED WITH THE FEATURE AND LACKS A DEFINED SURFACE LOW. THE
12Z ECMWF IS IN THE MIDDLE OF THE STRENGTH DEPICTED BY THE 00Z GFS
AND 12Z UKMET. A 3-WAY BLEND OF THE 00Z GFS, 12Z ECMWF AND 12Z
UKMET LOOKS REASONABLE BUT MINDING THE DIFFERENCES IN STRENGTH OF
THE SHORTWAVE...WHICH EXTEND FROM THE SURFACE TO THE TROPOPAUSE.
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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