413
FXUS10 KWNH 200457
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1157 PM EST WED FEB 19 2020
VALID FEB 20/0000 UTC THRU FEB 23/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...POSITIVELY TILTED MID-LEVEL TROUGH AXIS APPROACHING THE EAST
COAST THURSDAY NIGHT...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z ECMWF, 12Z UKMET BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
AS A SHORTWAVE TROUGH AXIS TRACKS EAST DURING THE DAY ON THURSDAY
INTO THURSDAY NIGHT, A SURFACE LOW WILL ORGANIZE OFF OF THE
SOUTHEAST COAST. THE 00Z NAM IS A TAD STRONGER AND FARTHER NORTH
WITH THE LOW COMPARED TO THE REMAINING DETERMINISTIC AND ENSEMBLE
GUIDANCE. THE 12Z CMC STANDS OUT AS WELL WITH A MORE NORTHWARD AND
SLIGHTLY QUICKER TROUGH PROGRESSION OFF OF THE EAST COAST. THE
BETTER ENSEMBLE CLUSTERING AGREES BEST WITH A 00Z GFS, 12Z ECMWF
AND 12Z UKMET BLEND.
...CLOSED MID-LEVEL LOW REACHING THE SOUTHWESTERN U.S. EARLY
SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z ECMWF, 12Z UKMET BLEND (LEAST WEIGHT ON
ECMWF)
CONFIDENCE: AVERAGE
THE ENSEMBLES HAVE BEEN TRENDING SLOWER WITH THE CLOSED LOW FRIDAY
INTO SUNDAY MORNING ACROSS THE SOUTHWEST. THE LATEST GUIDANCE
SHOWS THE 12Z CMC MUCH FASTER THAN THE LATEST CLUSTERING OF
DETERMINISTIC AND ENSEMBLE GUIDANCE. MEANWHILE, THE 00Z NAM LOOKS
A BIG STRONGER THAN THE REMAINING CONSENSUS BUT APPEARS REASONABLE
WITH TIMING.
OF THE REASONABLY WELL CLUSTERED 00Z GFS, 12Z ECMWF AND 12Z UKMET,
THE 12Z ECMWF IS FASTEST, FOLLOWED BY THE 00Z GFS AND THEN THE 12Z
UKMET. GIVEN TRENDS OVER THE PAST 24 HOURS, PREFER TO STAY IN THE
MIDDLE TO SLOWER SIDE OF THE GUIDANCE, WHICH WOULD PUT LESS WEIGHT
ON THE 12Z ECMWF COMPARED TO THE 00Z GFS AND 12Z UKMET.
..MID-LEVEL SHORTWAVE NEARING THE PACIFIC NORTHWEST ON SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS, 12Z ECMWF, 12Z UKMET BLEND (LEAST WEIGHT ON
GFS)
CONFIDENCE: SLIGHTLY BELOW AVERAGE
LARGE DIFFERENCES IN THE DETERMINISTIC GUIDANCE EXIST WITH A
SHORTWAVE FORECAST TO NEAR THE PACIFIC NORTHWEST ON SUNDAY. THE
00Z NAM IS RATHER FLAT ALOFT AND FEATURELESS AT THE SURFACE WHILE
THE 12Z ECMWF/UKMET/CMC ARE RATHER WRAPPED UP WITH THE MID-LEVEL
SHORTWAVE AND SURFACE REFLECTION. THE ENSEMBLE MEANS ARE IN
REASONABLE AGREEMENT AND APPEAR TO MATCH BEST TO THE 12Z
ECMWF/UKMET WHILE THE 00Z GFS IS A SLOWER AND SLIGHTLY WEAKER
VERSION OF THE ECMWF/UKMET. A 3-WAY BLEND (00Z GFS, 12Z ECMWF, 12Z
UKMET) APPEARS BEST AT THIS TIME BUT WITH LESS WEIGHT ON THE
SOMEWHAT SLOWER/WEAKER 00Z GFS.
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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