918
FXUS10 KWNH 310759
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EST TUE DEC 31 2019
VALID DEC 31/0000 UTC THRU JAN 03/1200 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
08Z UPDATE: NO SIGNIFICANT CHANGES NOTED ACROSS THE CONUS WITH THE
REST OF THE 00Z GUIDANCE. AS SUCH, WILL CONTINUE WITH THE
PREFERENCES BELOW.
..GREAT LAKES AND NORTHEAST CLOSED LOW
..SURFACE LOW TRACKING ALONG NEW ENGLAND COASTLINE TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
AS THE UPPER LEVEL LOW WEAKENS/OPENS UP OVER THE NORTHEAST U.S.
OVER THE NEXT 24-36 HOURS, A SECONDARY SURFACE LOW WILL DEVELOP
OFF THE MID-ATLANTIC TO NEW ENGLAND COAST. EARLIER DIFFERENCES
WITH THE TRACK/TIMING (GFS FASTER) HAVE DIMINISHED WITH THE MOST
RECENT GUIDANCE NOW SHOWING FAIRLY TIGHT CLUSTERING OF SOLUTIONS.
AS A RESULT, THERE IS HIGH ENOUGH FORECAST CONFIDENCE AND
CONSISTENCY TO GO WITH A GENERAL MODEL BLEND FOR THIS REGION.
..CLOSED LOW ENTERING MEXICO AND WEAKENING WEDNESDAY NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-CMC BLEND
CONFIDENCE: AVERAGE
TIMING DIFFERENCES ARE STILL APPARENT AS A CLOSED LOW ENTERS
MEXICO ON WEDNESDAY, WITH THE MOST RECENT GUIDANCE SHOWING THE
SIGNIFICANT SLOW BIAS OF THE 12Z CMC. THE 00Z GFS AND NAM SHOW
SIMILARITIES AT 500 MB TO THE ECMWF/UKMET THROUGH ABOUT 60 HOURS,
THEN THE NAM BECOMES A BIT SLOWER THAN THE OTHER GUIDANCE. FOR
NOW, WILL LEAN ON A NON-CMC BLEND GIVEN ITS DELAYED/SLOW SCENARIO.
...ATMOSPHERIC RIVER SINKING INTO PAC NW TONIGHT AND AMPLIFYING
INTO LONGWAVE TROUGH ACROSS THE CENTRAL U.S. THURSDAY EVENING...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND THROUGH 03.00Z FOLLOWED BY A
ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
THERE'S FAIRLY GOOD MODEL AGREEMENT AND RUN TO RUN CONSISTENCY
SEEN IN THE ATMOSPHERIC RIVER EVENT HEADING FOR THE PACIFIC NW THE
NEXT 24-36 HOURS. AS THE SHORTWAVE DIGS ACROSS THE WEST AND
EVENTUALLY CARVES OUT A LONGWAVE TROUGH FOR THE CENTRAL U.S.
MID/LATE WEEK, A SURFACE LOW IS FORECAST DEVELOP IN THE VICINITY
OF TX/OK. WITH THE NEUTRAL TO SLIGHTLY POSITIVE TILTED TROUGH IN
PLACE, WAVY LOW PRESSURE SHOULD LIFT ALONG THE SOUTH-CENTRAL
PLAINS TO MID-MS RIVER VALLEY. THERE ARE SOME NOTABLE DIFFERENCES
IN THE LOW TRACK/POSITION. THE LOW TRACK PLOTS AT 03.00Z AND
03.12Z SHOW SIZABLE SPREAD THAT LOWERS OVERALL FORECAST
CONFIDENCE. A CONSENSUS APPROACH IS APPROPRIATE FOR THE FIRST 60
HOURS (GENERAL MODEL BLEND) BUT THEN A ECMWF/UKMET/GFS BLEND IS
PREFERRED, GIVEN THE CMC'S TIMING BIAS.
...SHORTWAVE TROUGH AND SURFACE LOW APPROACHING PACIFIC NORTHWEST
FRIDAY/SATURDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: ECMWF/UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE
AFTER A BRIEF PERIOD OF RIDGING, ANOTHER SHORTWAVE TROUGH
APPROACHES THE PACIFIC NORTHWEST LATE IN THE WEEK INTO THIS
WEEKEND. THERE ARE CONSIDERABLE TIMING DIFFERENCES TYPICALLY SEEN
IN THE GUIDANCE, WHERE THE GFS IS MUCH FASTER COMPARED TO THE
NON-NCEP GUIDANCE. THE 00Z GFS RACES OUT AHEAD OF MOST OF THE
GUIDANCE AND IS SIGNIFICANTLY FASTER THAN THE GEFS MEAN AS WELL
(WHICH IS CLOSE TO THE ECMWF/ECENS SOLUTION). AS SUCH, WILL FAVOR
THE NON-NCEP GUIDANCE WITH A ECMWF/UKMET BLEND PREFERENCE.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.HTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
TAYLOR
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