779
FXUS10 KWNH 041913
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
213 PM EST WED DEC 04 2019
VALID DEC 04/1200 UTC THRU DEC 08/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND, LESS WEIGHT ON 12Z GFS/CMC
PARTICULARLY BY DAY 3
CONFIDENCE: ABOVE AVERAGE
DETERMINISTIC MODEL AGREEMENT CONTINUES TO BE QUITE GOOD OVER THE
NEXT FEW DAYS, WITH ENSEMBLE SPREAD RELATIVELY LOW. THIS SUGGESTS
A PATTERN WITH A RELATIVELY HIGH DEGREE OF PREDICTABILITY. THE 00Z
ECMWF ENSEMBLE 500MB SPREAD WAS FORECAST TO BE WELL BELOW THE
PREVIOUS 30-DAY AVERAGE OVER LARGE SWATHS OF THE CONUS BY LATE IN
THE WEEK, AND THE DETERMINISTIC MODELS REMAINED GENERALLY SITUATED
WELL WITHIN THE ENVELOPE OF ENSEMBLE VARIABILITY.
LESS WEIGHT WAS GRADUALLY PLACED ON THE 12Z RUNS OF THE GFS AND
CMC DURING THE FORECAST PERIOD, AND PARTICULARLY BY DAY 3 (FRIDAY
NIGHT AND SATURDAY). THE 12Z RUN OF THE GFS WAS SHOWING SIGNS OF
ITS LOW HEIGHT BIAS, PARTICULARLY IN THE SOUTHERN TIER OF STATES,
AS ITS HEIGHT PATTERN FALLS NEAR THE SOUTHERN EXTENT OF ENSEMBLE
VARIABILITY (AND IN SOME CASES OUTSIDE OF THAT
ENVELOPE)...ALTHOUGH THE BIAS WAS NOT QUITE AS PRONOUNCED AS IT
WAS IN THE 00Z AND 06Z RUNS. FURTHERMORE, THE GFS IS SHOWING A
FASTER PROGRESSION OF A TROUGH INTO THE WEST COAST THIS WEEKEND
ALONG WITH THE LATEST CMC. THIS IS IN CONFLICT WITH THE OTHER
DETERMINISTIC MODELS, THE AVAILABLE ENSEMBLE MEANS (INCLUDING THE
06Z GEFS WHICH IS SLOWER), AND THE TREND OVER THE PAST SEVERAL
MODEL CYCLES TOWARD A SLOWER SCENARIO.
THEREFORE, THE PREFERENCE IS FOR A GENERAL MODEL BLEND,
INCREASINGLY WEIGHTED TOWARD THE 12Z ECMWF, 00Z ECMWF ENSEMBLE,
12Z UKMET AND 12Z NAM BY THE WEEKEND.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
LAMERS/BANN
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