487
FXUS10 KWNH 240645
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST MON FEB 24 2020
VALID FEB 24/0000 UTC THRU FEB 27/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...MID-LEVEL SHORTWAVE AND ATTENDANT FRONT CLIPPING THE GREAT
LAKES/NORTHERN ME THROUGH MON...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. NO SIGNIFICANT CHANGES
WERE NOTED WITH THE 00Z ECMWF/UKMET/CMC COMPARED TO THEIR PREVIOUS
12Z CYCLES.
...OK/KS CLOSED LOW AND ITS INTERACTION WITH AN UPSTREAM
AMPLIFYING NORTHERN STREAM WAVE ACROSS PLAINS/GREAT LAKES
MON/TUESDAY...
...ASSOCIATED SURFACE LOW CROSSING THE MISSISSIPPI RIVER AND INTO
THE GREAT LAKES TUE/WED...
..DEVELOPING EAST COAST LOW WED NIGHT.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF, BLENDED WITH THE NON 00Z GFS DETERMINISTIC
GUIDANCE
CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE AFTER
..07Z UPDATE
NO SIGNIFICANT CHANGES WERE NOTED WITH THE CLOSED LOW AS IT
WEAKENS EAST INTO THE OHIO RIVER VALLEY THROUGH TUESDAY MORNING.
REGARDING THE UPSTREAM, LARGE SCALE TROUGH, THE 00Z UKMET TRENDED
A LITTLE SLOWER, WHILE THE 00Z CMC TRENDED A LITTLE FASTER
COMPARED TO THEIR 12Z CYCLES. THE 00Z ECMWF ALSO TRENDED SLOWER
AND SLIGHTLY WEAKER WITH THE TROUGH PROGRESSION BEGINNING TUESDAY
AFTERNOON.
FROM TUESDAY THROUGH THURSDAY MORNING, THE 00Z DETERMINISTIC
GUIDANCE SHOWS REASONABLE AGREEMENT OUTSIDE OF THE FASTER 00Z GFS,
THOUGH MINOR NON-GFS DIFFERENCES REMAIN. GIVEN SOME OF THE CHANGES
FROM CYCLE TO CYCLE, THE FINAL PREFERENCE WILL NOT BE TO JUMP
COMPLETELY ON BOARD WITH THE NON 00Z GFS SUITE OF MODELS (DESPITE
THEIR RELATIVE AGREEMENT), BUT TO NUDGE IN THAT DIRECTION FROM THE
12Z ECMWF POSITION. THEREFORE, THE FINAL PREFERENCE IS TO TAKE THE
12Z ECMWF AND BLEND IT WITH A 00Z ECMWF/UKMET/CMC/NAM BLEND.
..PREVIOUS DISCUSSION FOLLOWS
..12Z/24 UNTIL 12Z/25
REGARDING THE CLOSED LOW CURRENTLY NEAR THE KS/OK BORDER, THE
MODELS SHOW REASONABLE AGREEMENT ON THIS FEATURE QUICKLY WEAKENING
TOWARD THE ENE INTO THE OHIO VALLEY THROUGH MONDAY NIGHT. THE
RELATED SURFACE LOW WILL REACH SOUTHWESTERN IN AROUND 12Z/25, AND
THE SCATTER LOW ENSEMBLE LOW PLOTS HAVE BEEN FAIRLY CONSISTENT
WITH THIS POSITION SO CONFIDENCE IN A GENERAL MODEL BLEND IS GOOD
UP UNTIL THIS POINT INTO THE OHIO VALLEY.
FARTHER WEST, AN AMPLIFYING TROUGH WILL BEGIN TO REACH THE CENTRAL
PLAINS BY TUESDAY MORNING, WITH THE 12Z UKMET/CMC STRAYING EARLY
FROM THE ENSEMBLE MEAN AND REMAINING DETERMINISTIC CONSENSUS.
WHILE THE 00Z GFS BEGINS TO PULL AHEAD BY 12Z/25 OVER THE CENTRAL
PLAINS AT 500 MB, A 00Z NAM, 00Z GFS AND 12Z ECMWF BLEND WILL BE
REASONABLE.
..12Z/25 UNTIL 12Z/26
AS THE SYSTEM EVOLVES, THE MODEL CONSENSUS IS FOR A SMALL CLOSED
LOW AND POSITIVELY TILTED TROUGH AXIS EXTENDING SOUTHWEST FROM THE
LOW TO SWEEP TOWARD THE SOUTH AND EAST. THE 00Z GFS IS A BIT
FASTER THAN THE REMAINING MODEL CONSENSUS, WHILE THE 00Z NAM
BECOMES SLOWER AND THE 12Z ECMWF PLACED SOMEWHERE IN THE MIDDLE
BUT CLOSER TO THE GFS THAN NAM. MEANWHILE, THE 12Z UKMET IS A BIT
WEAKER AND SOUTH WITH THE MID-LEVEL CORE OF THE TROUGH, AND THE
12Z CMC IS SLOWER. A 3-WAY BLEND OF THE 00Z NAM, 12Z ECMWF AND 00Z
GFS IS PREFERRED HERE, BUT WITH LESS WEIGHT ON THE 00Z NAM BY
12Z/26.
..12Z/26 UNTIL 12Z/27
AS THE CENTER OF THE MID-LEVEL LOW LIFTS THROUGH THE GREAT LAKES,
INTERACTION OCCURS WITH AN UPPER TROUGH TO THE NORTH. THE LEAD
SHORTWAVE WILL QUICKLY SWING EAST WHILE COASTAL LOW DEVELOPMENT
OCCURS ALONG THE MID-ATLANTIC COAST. THE ENSEMBLE MEANS ARE IN
GOOD AGREEMENT, ALTHOUGH TRENDS IN THE ENSEMBLES HAVE BEEN FASTER
OVER THE PAST FEW CYCLES. THE CURRENT ENSEMBLE MEAN PLACEMENT IS A
LITTLE SLOWER THAN A 00Z GFS/12Z ECMWF BLEND. THE 00Z GFS IS
FASTEST, FOLLOWED BY THE 12Z ECMWF AND THEN THE SLOWER 00Z NAM.
THE GFS AND NAM HAVE TRENDED A LITTLE SLOWER WITH THEIR 00Z CYCLES
SO THIS IS IN CONTRAST TO ENSEMBLE TRENDS.
PLACEMENT NEAR THE 12Z ECMWF IS CONSIDERED BEST BUT WITH SOME
INCORPORATION OF THE 00Z NAM AND 00Z GFS.
...MID-LEVEL SHORTWAVE TROUGH/SURFACE COLD FRONT CLIPPING THE
PACIFIC NORTHWEST ON TUESDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
...07Z UPDATE..
NO SIGNIFICANT CHANGES WERE NOTED WITH THE 00Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 12Z CYCLES.
..PREVIOUS DISCUSSION FOLLOWS
THE MODELS ARE IN REASONABLE AGREEMENT WITH THE SHORTWAVE AND COLD
FRONT THAT ENTER BRITISH COLUMBIA AND NORTHERN WASHINGTON, MOVING
INTO A STRONG MID-LEVEL RIDGE. THERE ARE SOME MINOR LONGITUDE
DIFFERENCES WITH THE SHORTWAVE AS IT REACHES THE GREAT PLAINS ON
THE LEE SIDE OF THE RIDGE AXIS, BUT AT LEAST THROUGH THE END OF
THE SHORT RANGE PERIOD (12Z/27), A GENERAL MODEL BLEND WILL WORK
FOR THIS SYSTEM.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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