655
FXUS10 KWNH 060454
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1153 PM EST THU DEC 05 2019
VALID DEC 06/0000 UTC THRU DEC 09/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..OVERALL PATTERN ACROSS THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/12Z ECMWF WITH INCLUSION OF THE 00Z NAM IN
SOUTHERN STREAM
TRANSITIONING TO ECENS/GEFS MEAN BLEND FOR CENTRAL/EASTERN
CONUS AFTER 72HRS.
CONFIDENCE: SLIGHTLY ABOVE AVERAGE UNTIL 72HRS...SLIGHTLY BELOW
AFTERWARD EAST OF 100W.
MODEL AGREEMENT CONTINUES TO BE VERY STRONG ACROSS THE CONUS,
PARTICULARLY THROUGH 48HRS (08.00Z SUNDAY). MODEL SPREAD
INCREASES AFTER THIS POINT AS THE LARGE CLOSED LOW OFF THE N CA
COAST BREAKS DOWN SLOWLY WITH SOME INFUSION OF NORTHERN STREAM
ENERGY, BEFORE THE NORTHERN STREAM BEGINS TO DECOUPLE AND
ACCELERATE EASTWARD. THIS MODEL SPREAD IS CONTINGENT ON HOW MUCH
ENERGY SHEDS SOUTHWARD AND HOW FAST THE LEAD NORTHERN STREAM
SLIDES INTO THE NORTHERN PLAINS. THE 12Z ECMWF/ECENS HAVE SHOWN
THE MOST RUN TO RUN CONSISTENCY, HOWEVER, DID DEPICT A SLIGHTLY
FASTER SOLUTION THROUGH THE NORTHERN PLAINS, ATYPICAL OF ITS BIAS.
THE STICKING POINT WAS THE STRENGTH OF THE JET BEHIND THE WAVE
TO THE STRENGTH/AMPLIFICATION SWINGING OUT OF THE ARCTIC WITH A
MORE CONCENTRATED ARCTIC COLD POOL, WHICH NO OTHER SOLUTION
APPEARED TO DEPICT AS STRONG. THE 00Z GFS, HOWEVER, SHIFTED
ALMOST IN SYNC WITH THE EC/ECENS MEAN WITH A STRONGER ARCTIC
SHORTWAVE, FASTER TRANSLATION THROUGH THE NORTHERN
PLAINS...BUILDING CONFIDENCE TOWARD A BLEND WITH GFS INCORPORATION
(ECMWF/GFS BLEND).
THE REINVIGORATED CLOSED LOW, WILL DROP SOUTH ALONG THE CA COAST,
WITH MORE TYPICAL TIMING DIFFERENCES... AS THE 00Z GFS/12Z UKMET
OUTPACE THE 12Z ECMWF/NAM. THE GFS HOWEVER, DID TREND A BIT
SLOWER ADDING ADDITIONAL CONFIDENCE TOWARD THE SLOWER ECMWF/NAM.
HOWEVER, THE KNOWN BIAS OF THE ECMWF/NAM ARE SLOWER MORE COMPACT
SOLUTIONS BY THE END OF DAY 3...ESPECIALLY AS THE ECENS MEAN/GEFS
MEAN ARE MORE PROGRESSIVE. AS SUCH A 00Z GFS/NAM AND ECMWF BLEND
IS MORE FAVORED IN THE SOUTHERN STREAM, EVEN AS PIECES EMERGE INTO
THE CENTRAL CONUS.
BY THE END OF DAY THREE, A BROAD BUT DEEPENING SURFACE LOW/TROF
EXTENDS FROM THE GREAT LAKES TO THE SOUTHERN PLAINS, UNDER
INFLUENCE OF THE NORTHERN STREAM DIGGING ACROSS THE PLAINS, AND
BROAD HEIGHT-FALLS/ BROAD 250MB JET PROVIDE LARGE SCALE, LESS
FOCUSED ASCENT BY 12Z MONDAY. WHILE THE LARGER SCALE PATTERN IS
COMING INTO AGREEMENT, SMALL TIMING, PLACEMENT DIFFERENCES OF THE
INTERNAL SHORTWAVE FEATURES/PIECES LEAD TO LARGE VARIATION IN THE
QPF/THERMAL PROFILES ACROSS THE EASTERN US. THIS EVEN INCLUDES,
UNCERTAINTY IN THE AXIS OF STRENGTHENING EASTERN ATLANTIC RETURN
FLOW (WEAK SHORTWAVE), AFFECTING THE EASTERN CAROLINAS MONDAY
MORNING. THIS WOULD FAVOR HEDGING TOWARD THE ENSEMBLE MEANS TO
PULL OUT MEANINGFUL/BEST CLUSTERING OF AXIS OF QPF/FORCING AT
RELATIVELY LOW CONFIDENCE AT THIS POINT (EVEN THOUGH THE LARGER
SCALE PATTERN IS AGREEABLE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
GALLINA
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