026
FXUS10 KWNH 210651
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
151 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 MODEL EVALUATION WITH FINAL PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...CLOSED MID LEVEL LOW REACHING THE CENTRAL/SOUTHERN ROCKIES
SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z/00Z ECMWF, 00Z CMC BLEND (LEAST WEIGHT ON
CMC)
CONFIDENCE: AVERAGE
COMPARING THE PAST 4 CYCLES (12Z/00Z) OF THE ENSEMBLES, TRENDS
HAVE BEEN SLOWER EXCEPT FOR THE 12Z/20 CYCLE WHICH EDGED SLIGHTLY
FASTER. TIMING DIFFERENCES REMAIN WITH THE LATEST DETERMINISTIC
GUIDANCE, BUT THE 00Z UKMET STANDS OUT AS SLOWEST, DESPITE A
FASTER TREND COMPARED TO ITS PREVIOUS 12Z CYCLE WHICH WAS AN
ALMOST NEAR-OUTLIER WITH RESPECT TO THE LATEST ENSEMBLE GUIDANCE.
THE 00Z GFS SLOWED DOWN FROM ITS PREVIOUS 12Z CYCLE BUT REMAINS A
BIT AHEAD OF THE 00Z ECMWF/12Z 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 00Z ECMWF AND 00Z CMC BOTH ADJUSTED A LITTLE SOUTH COMPARED TO
THEIR PRIOR 12Z CYCLES BUT THE 00Z ECMWF IS A TAD SOUTH OF THE
BETTER ENSEMBLE MEAN CLUSTERING WITH THE 00Z ECMWF A TAD SLOWER AS
WELL. THE CHANGES IN THE 00Z ECMWF ARE NOT ENOUGH TO RULE IT OUT
BY ANY MEANS, BUT INCLUSION OF THE 12Z/20 ECMWF IS PREFERRED.
THE MIDDLE GROUND IS BEST REPRESENTED BY A 00Z GFS, 12Z/00Z ECMWF
AND 00Z CMC BLEND WITH THE BLENDED POSITION OF THE 700-850 MB LOW
CLOSE TO THE LATEST GEFS/ECMWF MEANS.
...WEAK MID-LEVEL SHORTWAVE AND ATTENDANT COLD FRONT REACHING THE
GREAT LAKES REGION ON SUNDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM 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 GUIDANCE HAS
LOCKED IN BETTER WITH THE DETAILS AND MAKE THE 00Z NAM STAND OUT
AS A SLOWER OUTLIER WITH THE SPEED OF THE SHORTWAVE. GIVEN THE
LATEST QUASI-AGREEMENT AMONG THE 00Z ECMWF/UKMET/CMC, IN LINE WITH
THE 00Z GFS, A NON 00Z NAM BLEND WILL BE PREFERRED WITH THIS
SYSTEM. THIS BLEND LIES TOWARD THE MIDDLE OF THE SPREAD GIVEN THE
LATEST ENSEMBLE DISTRIBUTION.
..MID LEVEL SHORTWAVE CROSSING THE PACIFIC NORTHWEST SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 00Z NAM BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THE 00Z NAM BECOMES SLOW TO MOVE THE SHORTWAVE EAST TOWARD
VANCOUVER ISLAND EARLY ON SUNDAY. THE 00Z GFS IS THE MOST
AMPLIFIED WITH THE BASE OF THE TROUGH AS IT MOVES INTO THE
NORTHERN GREAT BASIN BUT THE 00Z ECMWF/CMC HAVE TRENDED TOWARD THE
GFS IDEA, JUST NOT AS DEEP. GIVEN THE LATEST AVAILABLE GUIDANCE,
THE 00Z NAM STANDS OUT FOR MORE THAN JUST EARLY IN THE FORECAST
WITH A SLOWER TRACK AND LESS AMPLIFICATION INTO THE WEST BY MONDAY
MORNING. THE 00Z UKMET BACKED OFF FROM ITS PREVIOUS 12Z CYCLE
WHICH MORE CLOSELY MATCHED THAT OF THE 00Z GFS.
A NON 00Z NAM BLEND IS PREFERRED FOR THIS SYSTEM, WITH ONLY
RELATIVELY MINOR AMPLITUDE/TIMING DIFFERENCES INTO THE
NORTHWESTERN U.S.
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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