565
FXUS10 KWNH 191646
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1145 AM EST THU DEC 19 2019
VALID DEC 19/1200 UTC THRU DEC 23/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH PREFERENCE AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..SOUTHERN STREAM TROUGH CROSSING THE SOUTHWEST TODAY
..CROSSING THE SOUTHERN PLAINS/GULF COAST STATES FRI/SAT
..CYCLOGENESIS OVER THE GULF OF MEXICO
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z NAM/00Z UKMET AND 00Z ECMWF
CONFIDENCE: AVERAGE
A SOUTHERN STREAM TROUGH ADVANCING ACROSS THE SOUTHWEST TODAY WILL
CROSS THE SOUTHERN PLAINS AND GULF COAST STATES THROUGH SATURDAY
WHILE DRIVING CYCLOGENESIS OVER THE CENTRAL GULF OF MEXICO. THIS
SYSTEM WILL MOVE INTO THE SOUTHEAST ON SUNDAY. GENERALLY SPEAKING,
AND FITTING IN WITH ITS BIAS, THE 12Z GFS AND LATEST GEFS MEMBER
SUITE AGAIN APPEAR TO BE TOO PROGRESSIVE WITH THE EVOLUTION OF
THIS SYSTEM AS IT IMPACTS THE GULF COAST AND SOUTHEAST GOING
THROUGH THE WEEKEND. THE 00Z CMC IS ALSO AN OUTLIER WITH ITS
CLOSED LOW PLACEMENT MUCH FARTHER NORTH AND EAST OF THE MODEL
CONSENSUS BY THE END OF THE PERIOD. THE BETTER ENSEMBLE (00Z ECENS
SUITE) AND DETERMINISTIC CLUSTERING SUGGESTS A SLOWER SOLUTION
THAT IS CLOSE TO A BLEND OF THE 12Z NAM, 00Z UKMET AND 00Z ECMWF
AT THIS POINT, AND SO A BLEND OF THESE SLOWER SOLUTIONS WILL BE
PREFERRED.
..NORTHERN STREAM TROUGH CROSSING THE NORTHERN PLAINS/MIDWEST
..ENERGY ARRIVING ACROSS THE GREAT LAKES/NORTHEAST BY SAT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: ABOVE AVERAGE
A NORTHERN STREAM SHORTWAVE WILL ADVANCE DOWNSTREAM ACROSS THE
NORTHERN PLAINS AND MIDWEST THROUGH FRIDAY. THEREAFTER THE ENERGY
WILL PROGRESSIVELY CROSS THE GREAT LAKES AND NORTHEAST. THE 12Z
NAM APPEARS TO BE A BIT TOO SLOW AND TOO DEEP AS THE SYSTEM
ARRIVES ACROSS THE NORTHEAST, AND SO A NON-NAM BLEND WILL BE
PREFERRED WITH THIS SYSTEM.
..DEEP UPPER TROUGH OFFSHORE THE WEST COAST
..ATMOSPHERIC RIVER IMPACTING THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z UKMET/ECMWF AND 00Z ECENS/06Z GEFS MEAN BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
PERSISTENT LOW-LEVEL SOUTHWEST FLOW WILL BE IMPACTING THE COASTAL
RANGES OF WASHINGTON/OREGON AS MULTIPLE WAVES OF LOW PRESSURE RIDE
NORTHEAST UP ALONG AN OFFSHORE FRONTAL ZONE ASSOCIATED WITH AN
AMPLIFYING UPPER TROUGH. ONE FRONTAL WAVE WILL APPROACH VANCOUVER
ISLAND BY LATE THIS AFTERNOON, WITH A MORE SUBTLE WAVE APPROACHING
BY FRIDAY MORNING A BIT FARTHER SOUTH DOWN TOWARD COASTAL AREAS OF
NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THERE IS VERY MODEST
SPREAD WITH THE TIMING/DEPTH DETAILS OF THESE WAVES, BUT
REGARDLESS, THE MODELS ALL AGREE ON BRINGING VERY STRONG ONSHORE
FLOW/ATMOSPHERIC RIVER CONDITIONS INTO THE COASTAL RANGES AS A
SOUTHWEST LOW-LEVEL JET OF AS MUCH AS 70+ KTS IS EXPECTED TO BE
ARRIVING JUST AHEAD OF THE FRONT AND THESE SURFACE WAVES GOING
THROUGH FRIDAY MORNING. ADDITIONAL WAVE ACTIVITY IS FORECAST TO
LIFT UP ALONG THE FRONT FRIDAY NIGHT AND SATURDAY AS THE FRONT
SETTLES SLOWLY SOUTHEASTWARD AND BEGINS TO EDGE INLAND FARTHER
SOUTH DOWN ACROSS NORTHWEST CALIFORNIA. THE MODELS ALL BRING THE
UPSTREAM TROUGH BODILY INLAND ACROSS THE WEST COAST BY SUNDAY. THE
12Z GFS AND PERHAPS TO SOME EXTENT THE 12Z NAM APPEAR TO BE A TAD
TOO PROGRESSIVE WITH THE ENERGY ADVANCING INLAND (ESPECIALLY
RELATIVE TO CALIFORNIA). MEANWHILE, THE 00Z CMC IS LIKELY A LITTLE
TOO SLOW. THE BETTER MODEL CLUSTERING WOULD TEND TO FAVOR THE 00Z
UKMET/ECMWF SOLUTIONS WHICH HAVE GOOD SUPPORT FROM THE 00Z ECENS
MEAN AND 06Z GEFS MEAN, AND SO A BLEND OF THESE SOLUTIONS WILL BE
PREFERRED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
ORRISON
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