140
FXUS10 KWNH 301844
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
143 PM EST MON DEC 30 2019
VALID DEC 30/1200 UTC THRU JAN 03/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z MODEL EVALUATION WITH FINAL PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..GREAT LAKES AND NORTHEAST CLOSED LOW
..SURFACE LOW TRACKING ALONG NEW ENGLAND COASTLINE ON TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z GFS BLEND THROUGH 00Z/01, GENERAL MODEL BLEND
AFTERWARD
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
..19Z UPDATE
NO SIGNIFICANT CHANGES WERE NOTED WITH THE 12Z ECMWF/UKMET/CMC
COMPARED TO THEIR PREVIOUS 00Z CYCLES. NO CHANGES ARE RECOMMENDED
FOR THE FINAL PREFERENCE.
..PREVIOUS DISCUSSION FOLLOWS
THE MORE SIGNIFICANT DIFFERENCES WITH THIS SYSTEM PERTAIN TO THE
SECONDARY SURFACE LOW TRACKING ALONG THE NEW ENGLAND COAST FOR
TUESDAY. THE 12Z GFS WAS WEAKER (NOTED AT 925 MB) WITH THE LOW
RESULTING IN LESS LOW LEVEL NORTHERLY FLOW INTO THE NORTHEAST. BY
TUESDAY EVENING HOWEVER (00Z/01), THE DIFFERENCES BECOME LESS
NOTICEABLE AS THE LOW DEEPENS AND PULLS AWAY FROM THE LOWER 48.
..CLOSED LOW ENTERING MEXICO AND WEAKENING WEDNESDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NEAR THE 12Z ECMWF
CONFIDENCE: AVERAGE
..19Z UPDATE
ONLY MINOR ADJUSTMENTS WERE OBSERVED WITH THE 12Z NON-NCEP
GUIDANCE RELATIVE TO THEIR PREVIOUS 00Z CYCLES. THERE WERE SOME
ADJUSTMENTS TO THE TIMING OF THE SUBSEQUENT LONGWAVE TROUGH
HOWEVER, WHICH ARE DISCUSSED BELOW.
..PREVIOUS DISCUSSION FOLLOWS
TIMING DIFFERENCES ARE APPARENT AS A CLOSED LOW ENTERS MEXICO ON
WEDNESDAY WITH THE 12Z GFS LEADING THE PACK WITH A FASTER TRACK.
THE 00Z CMC ENDS UP SLOWER THROUGH THURSDAY MORNING. ENSEMBLE
TRENDS HAD BEEN A BIT FASTER BUT BACKED OFF ANY SIGNIFICANT TIMING
TREND WITH THE LAST CYCLE (INITIALIZED 00Z/30). THE FASTER
GFS/GEFS AND SLOWER CMC ARE REFLECTED IN THE LATEST ENSEMBLE
DISTRIBUTION WITH THE 00Z ECMWF/ECMWF MEAN NEAR THE MIDDLE. THE
PREFERENCE IS TO BE NEAR TO SLIGHTLY AHEAD OF THE MIDDLE GROUND,
OR NEAR THE 00Z ECMWF AT THIS TIME.
...ATMOSPHERIC RIVER SINKING INTO PAC NW TONIGHT AND AMPLIFYING
INTO LONGWAVE TROUGH ACROSS THE CENTRAL U.S. THURSDAY EVENING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND WEIGHTED TOWARD THE 00Z ECMWF
CONFIDENCE: SLIGHTLY BELOW AVERAGE
..19Z UPDATE
THE 12Z ECMWF AND 12Z UKMET SLOWED DOWN THE TIMING OF THE LONGWAVE
TROUGH AXIS APPROACHING THE GREAT PLAINS THURSDAY MORNING WHILE
THE 12Z CMC SPED UP...RELATIVE TO THEIR PREVIOUS 00Z CYCLES. THE
LATEST ENSEMBLE SPREAD SUPPORTS THE PRELIMINARY PREFERENCE GIVEN A
12Z NON-NCEP BLEND WEIGHTS TOWARD THE WESTERN SIDE OF THE LATEST
ENSEMBLE SPAGHETTI PLOTS BY THURSDAY EVENING.
..PREVIOUS DISCUSSION FOLLOWS
THERE ARE RELATIVELY MINOR DIFFERENCES WITH THE ATMOSPHERIC RIVER
EVENT INTO THE PACIFIC NORTHWEST EARLY ON WITH THE 12Z GFS WEAKER
AND SOUTH OF THE BETTER MODEL CLUSTERING VALID 00Z/01 TO THE NORTH
OF VANCOUVER ISLAND REGARDING A SURFACE LOW. THIS RESULTS IN A
SLIGHTLY WEAKER MAGNITUDE TO THE LOW LEVEL FLOW INTO WASHINGTON
AND OREGON. AS THE MID-LEVEL ENERGY EVOLVES DOWNSTREAM, A LONGWAVE
TROUGH FORMS OVER THE WEST-CENTRAL U.S. WITH A FEW EMBEDDED
SHORTWAVE IMPULSES. DIFFERENCES IN TIMING ARE NOTED WITH A 700 MB
TROUGH AXIS INTO THE CENTRAL U.S. BY THURSDAY EVENING WITH,
SIMILAR TO THE ABOVE SYSTEM, A 00Z ECMWF MIDDLE GROUND BEING
FAVORED.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
OTTO
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