Prognostic Meteorological Discussion
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000
FXUS10 KWNH 061706
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1205 PM EST TUE DEC 06 2016

VALID DEC 06/1200 UTC THRU DEC 10/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


WEAKENING VORT MAX REACHING THE MID-ATLANTIC COAST THIS EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

ONLY MINOR DIFFERENCES EXIST WITH THIS SYSTEM...BUT THEY ARE SMALL
ENOUGH TO SUPPORT A GENERAL MODEL COMPROMISE.


CLOSED LOW ALONG THE U.S.-CANADIAN BORDER THIS MORNING...LIFTING
  INTO QUEBEC ON THU
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE 12Z NAM STANDS OUT FROM THE REMAINING MODEL CONSENSUS WITH A
STRONG/SLOWER UPPER TROUGH IN SRN QUEBEC AS THE CLOSED LOW MOVES
INTO ERN CANADA THU EVENING. THE 12Z GFS LOOKS TOWARD THE FASTER
SIDE...BUT THERE IS SUPPORT FROM THE ENSEMBLE MEANS FOR A QUICKER
TRACK VERSUS SLOWER LIKE THE NAM. A 12Z GFS/00Z ECMWF BLEND
REPRESENTS THE BEST AVERAGE POSITION OF THE BETTER MODEL
CLUSTERING.


SHORTWAVE TROUGH TRACKING FROM THE GREAT BASIN TODAY...TO THE
  NORTHEAST COAST THU EVENING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF
CONFIDENCE: AVERAGE

THE 00Z ECMWF REPRESENTS THE MIDDLE OF THE TIMING SPREAD NOTED
WITH THE LATEST SUITE OF MODELS.


SERIES OF STORM SYSTEMS IMPACTING THE WEST COAST THU/FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF/UKMET BLEND
CONFIDENCE: BELOW AVERAGE

A CLOSED LOW IS FORECAST TO DEVELOP WEST OF THE PACIFIC NORTHWEST
COAST BY THU EVENING...FOLLOWED BY A MID-LEVEL SHORTWAVE TROUGH TO
REACH THE CNTRL TO NRN WEST COAST FRI EVENING. THE LATEST
ENSEMBLES SHOW A GREAT DEAL OF SPREAD WITH THIS SYSTEM WHICH
REDUCES CONFIDENCE. HOWEVER...ENOUGH SUPPORT OR LACK THEREOF
EXISTS TO RULE OUT SOME MODEL SOLUTIONS AS UNLIKELY.

FOR EXAMPLE...12Z GFS APPEARS TOO STRONG WITH A SMALL CLOSED LOW
NORTHWEST OF THE WASHINGTON/OREGON COAST THU EVENING...WITH LITTLE
ENSEMBLE SUPPORT. THE GFS SEEMS TOO WEAK WITH ITS SECOND CLOSED
LOW AS IT REACHES THE PACIFIC NORTHWEST COAST FRI
EVENING...RESULTING IN AN OPEN WAVE. LARGE DIFFERENCES WITH THE
STRENGTH OF THE RESULTING SURFACE LOW EXIST

THE ENSEMBLE MEANS ARE WEIGHTED MOST GIVEN THE LARGE SPREAD AND
RUN TO RUN VARIABILITY IN THE DETERMINISTIC MODELS...WITH THE 00Z
ECMWF AND 00Z UKMET LIKELY CLOSEST TO THE MEANS AT THIS TIME.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

$$





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