189
FXUS10 KWNH 111837
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
236 PM EDT WED MAR 11 2020
VALID MAR 11/1200 UTC THRU MAR 15/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..CLOSED LOW AFFECTING THE SOUTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF/CMC BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
ONLY VERY MINOR CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES, SO NO CHANGES ARE
RECOMMENDED FOR THE FINAL PREFERENCE.
..PREVIOUS DISCUSSION FOLLOWS
ENSEMBLE SPAGHETTI PLOTS SUGGEST THE 00Z UKMET IS TOO SLOW, ALONG
WITH THE 12Z NAM REGARDING THE WEAKENING MID-LEVEL CLOSED LOW AS
IT TRACKS ACROSS THE SOUTHWEST THROUGH SATURDAY MORNING. DURING
THE DAY ON SATURDAY, THE 12Z NAM BECOMES A SIGNIFICANTLY SLOWER
OUTLIER WITH THE MID-LEVEL SHORTWAVE, BECOMING 500-600 MILES
SLOWER THAN THE REMAINING MODEL CONSENSUS LATER IN THE DAY ON
SATURDAY. THE 12Z GFS, 00Z ECMWF AND 00Z CMC AGREE REASONABLY WELL
WITH ONE ANOTHER AND THE ENSEMBLE MEANS.
...NORTHERN STREAM TROUGH TRACKING FROM THE NORTHERN ROCKIES,
UPPER MIDWEST TOWARD THE NORTHEAST THROUGH FRIDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
ONLY VERY MINOR CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES, SO NO CHANGES ARE
RECOMMENDED FOR THE FINAL PREFERENCE.
..PREVIOUS DISCUSSION FOLLOWS
TIMING DIFFERENCES APPEAR WITH AN AMPLIFYING MID-LEVEL TROUGH
EXPECTED TO TRACK ACROSS THE GREAT LAKES REGION THURSDAY NIGHT.
THE 12Z NAM IS NOTABLY SLOWER WITH THE 00Z ECMWF/CMC A TOUCH
SLOWER AS WELL COMPARED TO THE ENSEMBLE MEANS. MEANWHILE, THE 12Z
GFS IS A LITTLE FASTER THAN THE ENSEMBLE MEANS REGARDING THE 500
MB TROUGH AND ASSOCIATED SPEED SHEAR ENHANCED VORTICITY MAX
ROUNDING THE BASE OF THE TROUGH.
ENSEMBLE SCATTER LOW PLOTS SHOW A FAIR DEGREE OF NORTH/SOUTH
SPREAD WITH THE SURFACE LOW CROSSING THE GREAT LAKES REGION INTO
ONTARIO. THE 00Z UKMET/CMC ARE TOWARD THE SOUTHERN SIDE OF THE LOW
TRACK SPREAD, ESPECIALLY THE 00Z UKMET. A BLEND OF THE 12Z GFS AND
00Z ECMWF APPEARS TO BE THE BEST COMPROMISE FOR THIS SYSTEM.
..CLOSED LOW DEVELOPING OVER PACIFIC NW FRIDAY/SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
ONLY VERY MINOR CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES, SO NO CHANGES ARE
RECOMMENDED FOR THE FINAL PREFERENCE.
..PREVIOUS DISCUSSION FOLLOWS
THE 12Z NAM IS THE ONLY MODEL TO SIGNIFICANTLY STAND OUT WITH AN
EVENTUAL CLOSED LOW TO AFFECT THE NORTHWESTERN U.S. FOR THE END OF
THE WEEK, WITH A DEEPER AND SLOWER PROGRESSION. THE NON 12Z-NAM
GUIDANCE IS REASONABLY SIMILAR BUT THE 12Z GFS IS NOTED TO BE
WEAKER WITH THE 700 MB LOW IN THE NORTHWEST COMPARED TO THE RATHER
AGREEABLE 00Z ECMWF/UKMET/CMC. DESPITE THE DIFFERENCES OF THE 12Z
GFS, AND COLDER LOW LEVEL AIR INTO MONTANA BY SATURDAY
MORNING/AFTERNOON, WHEN BLENDED WITH THE 00Z ECMWF/UKMET/CMC, A
PREFERRED BLEND IS REACHED.
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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