098
FXUS10 KWNH 131959
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 PM EST FRI DEC 13 2019
VALID DEC 13/1200 UTC THRU DEC 17/0000 UTC
...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...
12Z EVALUATION WITH PRELIMINARY PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
..EASTERN 2/3 OF THE CONUS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON-NAM BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
20Z UPDATE: NO SIGNIFICANT CHANGES NOTED WITH THE REST OF THE 12Z
GUIDANCE TO DEVIATE FROM THE CURRENT BLEND PREFERENCE.
A COUPLE OF SYSTEMS WILL WORK THROUGH THE EASTERN 1/3 CONUS OVER
THE NEXT 3 DAYS. IN THE NEAR TERM, A WAVE OF LOW PRESSURE AND
ASSOCIATED MID/UPPER LEVEL TROUGH WILL LIFT THROUGH THE EAST
COAST, BRINGING WIDESPREAD PRECIPITATION TO MUCH OF THE REGION. AN
AREA OF LOW PRESSURE WILL MOVE FROM NEAR THE GULF COAST TOWARD THE
MID-ATLANTIC AND THEN DEEPEN OVER THE NORTHEAST. THERE IS ABOVE
AVERAGE AGREEMENT WITH THE PLACEMENT, STRENGTH, AND TRACK OF LOW
THROUGH 60 HOURS.
A SECONDARY SYSTEM WILL DEVELOP LATER IN THE FORECAST PERIOD, AS
SHORTWAVE ENERGY FROM THE WEST COAST REACHES THE SOUTHERN/CENTRAL
PLAINS. A LOW PRESSURE IS FORECAST TO DEVELOP IN THE VICINITY OF
NORTH TEXAS AND THEN LIFT EAST/NORTHEAST TOWARD THE OHIO VALLEY BY
84 HOURS. HERE, THE 12Z NAM MASS FIELDS (PARTICULARLY THE SURFACE
LOW) IS WAY AHEAD OF THE REST OF THE DETERMINISTIC MODELS (16.12Z
LOW OVER CVG COMPARED TO THE REST OF THE MODELS WHICH HAVE A MEAN
POSITION OF LIT). HOWEVER, ALOFT, ITS 500 MB HEIGHTS AND VORTICITY
IS NOT SUBSTANTIALLY DIFFERENT AND THE RESULTANT QPF IS NOT TOO
MUCH OF AN OUTLIER COMPARED TO THE REST OF THE MODELS. SO, WHILE
THE PREFERENCE IS LEAN AWAY FROM THE NAM, IT IS NOT NECESSARILY
CONSIDERED AN OUTLIER.
..WESTERN 1/3 OF THE CONUS.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE
20Z UPDATE: NO SIGNIFICANT CHANGES NOTED WITH THE REST OF THE 12Z
GUIDANCE TO DEVIATE FROM THE CURRENT BLEND PREFERENCE.
SHORTWAVE TROUGH MOVES ONSHORE THE WESTERN US SATURDAY AND THEN
WILL BE FOLLOWED BY RIDGING ANCHORED ALL THE WAY THROUGH THE WEST
COAST OF CANADA TO END THE FORECAST PERIOD (MONDAY). OVERALL MODEL
AGREEMENT IS ABOVE AVERAGE FROM THE 500 MB HEIGHTS TO THE SURFACE
AS WELL AS QPF FIELDS. A GENERAL MODEL BLEND IS PREFERRED.
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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