804
FXUS10 KWNH 271652
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1152 AM EST WED NOV 27 2019
VALID NOV 27/1200 UTC THRU DEC 01/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST
CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/12Z NAM BLEND
CONFIDENCE: AVERAGE
AN AMPLIFIED PATTERN ACROSS THE LOWER 48 IS IN PLACE AT THE START
OF THE PERIOD WITH A POTENT CLOSED LOW OVER THE UPPER MIDWEST AND
A SECOND CLOSED LOW OVER THE PACIFIC NORTHWEST COAST. AS THE
EASTERN CLOSED LOW TRACKS EAST THROUGH THURSDAY, WITH ONLY MINOR
DIFFERENCES, THE FLOW TRANSITIONS TOWARD A DEEP TROUGH OVER THE
WESTERN HALF OF THE NATION WITH ANOMALOUS RIDGING DOWNSTREAM OVER
THE EAST FOR THURSDAY AND FRIDAY. A MID-LEVEL LOW WILL EJECT OUT
INTO NEBRASKA/SOUTH DAKOTA ON SATURDAY AS A PORTION OF THE
MID-LEVEL LOW HANGS BACK OVER THE PACIFIC NORTHWEST. ANOTHER
CLOSED LOW WILL NEAR THE WEST COAST LATE SATURDAY.
THE BIGGEST DIFFERENCES IN GUIDANCE LIE WITH THE LARGE WESTERN
CLOSED LOW WITH THE 12Z GFS STANDING OUT SIGNIFICANTLY FROM THE
REMAINING DETERMINISTIC GUIDANCE. THE GFS TRACKS THE CENTER OF THE
MID-LEVEL CLOSED LOW A BIT FARTHER SOUTH AND ENDS UP SLIGHTLY
FASTER THAN THE REMAINING MODEL CONSENSUS ON FRIDAY. AS A STRONG
SURFACE LOW DEVELOPS IN THE GREAT PLAINS FRIDAY NIGHT INTO
SATURDAY, THE GFS SURFACE LOW TRACKS FARTHER WEST/NORTH WHILE ALSO
BEING STRONGER THAN THE REMAINING MODEL GUIDANCE. LOW LEVEL WARM
AIR WRAPS UP SIGNIFICANT FARTHER NORTH THROUGH THE NORTH-CENTRAL
U.S. THAN NON-GFS GUIDANCE. WHILE THE 12Z GFS IS NOT AN OUTLIER
WITH RESPECT TO THE ENSEMBLE DISTRIBUTION, LACK OF CONSISTENCY AND
SUPPORT FROM THE GFS WARRANTS CAUTION IN ITS SOLUTION. THE ECMWF
MEAN AND DETERMINISTIC ECMWF HAVE BEEN FAIRLY CONSISTENT AND MATCH
CLOSER TO A NON-GEFS/GFS BLEND OF MODELS WITH THE BIGGER PICTURE
EVOLUTION OF THE STORM SYSTEM. THE 12Z NAM IS CLOSEST TO THE 00Z
ECMWF BUT THE SURFACE LOW IN THE NAM IS SLIGHTLY WEAKER THAN IDEAL
AND THE 12Z NAM MAY BE TOO COLD IN THE LOWER LEVELS. THE 00Z
UKMET/CMC LOOK OKAY AT TIMES, BUT DEVIATE ENOUGH FROM THE
PREFERRED MODEL BLEND TO EXCLUDE THEM FROM BEING INCLUDED IN THE
PREFERENCE.
LASTLY, THE CLOSED LOW APPROACHING CALIFORNIA AND OREGON LATE
SATURDAY SHOWS FAIR AGREEMENT AMONG THE LATEST MODELS, BUT THE 12Z
NAM, 12Z GFS AND 00Z ECMWF MATCH CLOSEST TO THE AGREEABLE ENSEMBLE
MEANS WHILE THE 00Z UKMET/CMC DIFFER ON TIMING. INTERACTION WITH
THE REMNANT PACIFIC NORTHWEST PORTION OF MID-LEVEL ENERGY FAVORS
MORE OF A 12Z NAM/00Z ECMWF BLEND OVER THE 12Z GFS.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
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