Prognostic Meteorological Discussion
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000
FXUS10 KWNH 050652
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 AM EST MON DEC 5 2016

VALID DEC 5/0000 UTC THRU DEC 8/1200 UTC

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

00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
MODEL INITIALIZATION ERRORS APPEAR NEGLIGIBLE WITH RESPECT TO
THEIR FORECASTS


NORTHERN MEXICO CLOSED LOW EJECTING NORTHEASTWARD TOWARDS THE EAST
COAST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~
PREFERENCE: 00Z ECMWF/GFS/UKMET COMPROMISE
CONFIDENCE: NEAR AVERAGE

THE UPPER LEVEL LOW CURRENTLY OVER NORTHERN MEXICO IS FORECAST TO
TRACK NORTHEASTWARD AND EVOLVE INTO A PROGRESSIVE OPEN WAVE ALOFT.
 AT THE SURFACE, A SURFACE LOW WILL TRACK INLAND WEST OF THE
APPALACHIANS WHILE ANOTHER LOW FORMS NEAR THE NORTH CAROLINA COAST
AND BECOME AN OFFSHORE GALE CENTRE LATER IN THE PERIOD.
MODEL SPREAD CONTINUES TO REDUCE WITH TIME AS THE UPPER LOW TRACKS
ACROSS NORTHERN MEXICO AND THEN OVER TEXAS BY MONDAY AFTERNOON.
THE 00Z NAM IS SLIGHTLY DEEPER WITH THE UPPER LOW BY TUESDAY
EVENING AS IT CROSSES EASTERN TEXAS AND SLIGHTLY SLOWER THAN THE
MODEL CONSENSUS.  THE 00Z ECWMF HAS TRENDED MORE AMPLIFIED WITH
THE OPEN WAVE ALOFT FROM 24 TO 48 HOURS.  THE 00Z UKMET IS CLOSER
TO THE MODEL CONSENSUS COMPARED TO ITS EARLIER RUN.


NORTHERN U.S. SHORTWAVE SHEARING OUT ACROSS NEW ENGLAND BY MONDAY
NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~
PREFERENCE: GENERAL MODEL BLEND
CONFIDENCE: ABOVE AVERAGE

A NEGATIVELY TILTED NORTHERN STREAM SHORTWAVE CURRENTLY OVER THE
GREAT LAKES IS FORECAST TO TRACK RAPIDLY EASTWARD TOWARDS NEW
ENGLAND ON MONDAY.  IT THEN SHEARS OUT WEST TO EAST OVER THE UPPER
LEVEL RIDGE DIRECTLY AHEAD OF IT, AND BY THE TIME IT REACHES NEW
ENGLAND IT BECOMES MORE ZONALLY ORIENTED.  THERE IS ENOUGH
AGREEMENT IN THE GUIDANCE TO SUPPORT A GENERAL MODEL BLEND WITH
ABOVE AVERAGE CONFIDENCE.


SOUTHERN CANADA CLOSED LOW WITH SURFACE LOW DEVELOPMENT OVER
NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~
PREFERENCE: 00Z NAM/00Z GFS/00Z UKMET BLEND
CONFIDENCE: SLIGHTLY BELOW AVERAGE

SHORTWAVE ENERGY CURRENTLY OVER THE NORTHERN ROCKIES WILL CONTINUE
TO ROTATE AROUND THE SOUTHERN PERIPHERY OF THE UPPER LEVEL VORTEX
THAT IS STARTING TO FORM OVER SASKATCHEWAN.  THE COLD FRONT
ASSOCIATED WITH THE SURFACE LOW WILL USHER IN THE FIRST NOTEWORTHY
ARCTIC AIRMASS OF THE SEASON.  GIVEN THE DOWNSTREAM UPPER LEVEL
CONFIGURATION, THE TIMING OF THIS SHORTWAVE WILL DETERMINE THE
MAGNITUDE OF DEEPENING OVER THE EASTERN DAKOTAS AND MINNESOTA BY
EARLY TUESDAY.  THE 00Z CMC IS CLOSER TO THE MODEL CONSENSUS WITH
THE UPPER LOW TUESDAY NIGHT COMPARED TO ITS EARLIER RUN, BUT STILL
MORE AMPLIFIED COMPARED TO THE OTHER GUIDANCE.  THE 00Z ECMWF IS
SLIGHTLY SLOWER THAN THE MODEL CONSENSUS WITH THE SURFACE LOW JUST
NORTH OF MINNESOTA.


SHORTWAVE TROUGH CROSSING THE GREAT BASIN TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z GFS/UKMET/ECMWF BLEND
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE GULF OF ALASKA UPPER LOW UNDER THE INFLUENCE OF A LARGER
GLOBAL SCALE TROUGH ACROSS NORTHWESTERN CANADA BEGINS TO SHEAR OUT
ALONG THE BRITISH COLUMBIA COAST ON MONDAY.  THE SHORTWAVE ENERGY
ASSOCIATED WITH THIS IS EXPECTED TO CROSS THE PACIFIC NORTHWEST
BEFORE SETTLING ACROSS THE GREAT BASIN ON TUESDAY, AND EJECTING
ACROSS THE CENTRAL PLAINS BY WEDNESDAY.  THE 00Z NAM BECOMES MORE
PROGRESSIVE WITH THE TROUGH AS IT CROSSES THE CENTRAL ROCKIES
TUESDAY NIGHT.  THE 12Z EC MEAN IS INITIALLY MORE PROGRESSIVE WITH
THE SHORTWAVE TROUGH AND FASTER THAN THE OPERATIONAL 00Z ECWMF
OVER THE PACIFIC NORTHWEST, BUT LATER IS CLOSER TO THE MODEL
CONSENSUS.



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

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

HAMRICK

$$




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