322
FXUS10 KWNH 210521
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1220 AM EST FRI FEB 21 2020
VALID FEB 21/0000 UTC THRU FEB 24/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CLOSED MID LEVEL LOW REACHING THE CENTRAL/SOUTHERN ROCKIES
SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z ECMWF, 12Z CMC BLEND (LEAST WEIGHT ON CMC)
CONFIDENCE: AVERAGE
COMPARING THE PAST 4 CYCLES (12Z/00Z) OF THE ENSEMBLES, TRENDS
WERE SLOWER EXCEPT FOR THE 12Z/20 CYCLE WHICH EDGED SLIGHTLY
FASTER. TIMING DIFFERENCES REMAIN WITH THE LATEST DETERMINISTIC
GUIDANCE, BUT THE 12Z UKMET STANDS OUT AS SLOWEST, AND AN ALMOST
NEAR-OUTLIER WITH RESPECT TO THE LATEST ENSEMBLE GUIDANCE. THE 00Z
GFS SLOWED DOWN FROM ITS PREVIOUS 12Z CYCLE BUT REMAINS SLIGHTLY
AHEAD OF THE 12Z ECMWF/ECMWF MEAN. THE 00Z NAM IS SLIGHTLY NORTH
AND A BIT STRONGER THAN THE REMAINING CONSENSUS WITH THE 700-500
MB LOW AS IT CROSSES THE ROCKIES.
THE MIDDLE GROUND IS BEST REPRESENTED BY A 00Z GFS, 12Z ECMWF AND
12Z CMC BLEND, BUT WITH THE LEAST WEIGHT ON THE CMC GIVEN ITS
700-850 MB LOW IS A BIT NORTH OF THE LATEST GEFS/ECMWF MEANS.
...WEAK MID-LEVEL SHORTWAVE AND ATTENDANT COLD FRONT REACHING THE
GREAT LAKES REGION ON SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF BLEND
CONFIDENCE: AVERAGE
THERE IS A FAIR AMOUNT OF MODEL SPREAD WITH A FAST MOVING
SHORTWAVE TO TRACK ACROSS SOUTHERN CANADA SATURDAY NIGHT THROUGH
SUNDAY NIGHT. WHILE MOISTURE IS LACKING WITH THIS SYSTEM, A COLD
FRONT WILL TRACK ACROSS THE NORTH-CENTRAL U.S., WITH THE
DIFFERENCES ALOFT TRANSLATING TO THE SURFACE. THE 00Z GFS AND 12Z
ECMWF ARE IN THE MIDDLE OF THE SPREAD, WHILE THE 00Z NAM AND 12Z
CMC ARE SLOWER AND 12Z UKMET FASTER. PREFER TO STAY TOWARD THE
MIDDLE OF THE SPREAD GIVEN THE LATEST ENSEMBLE DISTRIBUTION.
..MID LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z NAM, 12Z ECMWF, 12Z CMC BLEND (LEAST WEIGHT ON THE
NAM)
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 00Z NAM BECOMES SLOW TO MOVE THE SHORTWAVE EAST TOWARD
VANCOUVER ISLAND EARLY ON SUNDAY. THE 00Z GFS AND 12Z UKMET ARE
MORE AMPLIFIED WITH THE BASE OF THE TROUGH, WHILE THE 12Z ECMWF
AND 12Z CMC ARE CLOSER TO THE MEANS. BY MONDAY MORNING, THE 00Z
GFS AND 12Z UKMET STAND OUT WITH A DEEPER/SOUTHERN BASE OF THE
SHORTWAVE AMPLIFYING ACROSS THE GREAT BASIN, WHILE THE 00Z NAM
MATCHES CLOSER TO THE ENSEMBLE MEANS WITH TIMING ALONG WITH THE
12Z ECMWF/CMC. A 3-WAY BLEND OF THE 00Z NAM, 12Z ECMWF AND 12Z CMC
ARE CONSIDERED BEST BUT WITH LESS WEIGHT ON THE 00Z NAM GIVEN IT
IS SLOWER WITH THE TIMING OF THE SYSTEM EARLY ON SUNDAY.
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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