Prognostic Meteorological Discussion
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000
FXUS10 KWNH 090645
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
144 AM EST FRI DEC 9 2016

VALID DEC 9/0000 UTC THRU DEC 12/1200 UTC

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

00Z NAM/GFS MODEL EVALUATION ALONG WITH PREFERENCES AND CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
***00Z NAM INITIALIZED 850MB TEMPERATURES 3-4 DEGREES C TOO COLD
OVER PARTS OF THE PACIFIC NORTHWEST***

DEEP UPPER TROUGH SWINGING THROUGH THE NORTHEASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE LARGE SYNOPTIC SCALE TROUGH OVER THE NORTHEAST U.S. AT THE
BEGINNING OF THE PERIOD IS PROGGED TO MOVE OVER THE CANADIAN
MARITIMES BY FRIDAY.  GOOD OVERALL MODEL AGREEMENT EXISTS TO
SUPPORT A GENERAL MODEL COMPROMISE HERE.


LOW AMPLITUDE SHORTWAVE CROSSING THE GREAT LAKES AND NEW ENGLAND
THROUGH SATURDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~

PREFERENCE: 00Z NAM/00Z UKMET/00Z ECMWF COMPROMISE
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A COUPLE OF WEAK SHORTWAVES CURRENTLY OVER SOUTH-CENTRAL CANADA
SHOULD MIGRATE EASTWARD AND CONSOLIDATE INTO A LOW-AMPLITUDE
LONGWAVE TROUGH WHICH WILL MOVE ACROSS THE GREAT LAKES BY FRIDAY
NIGHT AND INTO SATURDAY.  THE 00Z CMC HAS TRENDED FASTER TOWARDS
THE MODEL CONSENSUS, WITH THE 00Z GFS NOW ONLY SLIGHTLY MORE
AMPLIFIED COMPARED TO ITS EARLIER RUN.  GIVEN THIS IMPROVED MODEL
AGREEMENT, A GENERAL MODEL COMPROMISE CAN ALSO BE ADVISED HERE.


PROGRESSIVE SHORTWAVE AND SURFACE LOW REACHING THE MIDWEST BY
MONDAY MORNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~

PREFERENCE: 12Z ECMWF/00Z ECMWF/00Z CMC COMPROMISE
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A SURFACE LOW TRACKING FROM THE LEE OF THE ROCKIES SATURDAY
AFTERNOON TO THE OHIO VALLEY BY MONDAY MORNING WILL BE SUPPORTED
BY A BROAD MID-LEVEL TROUGH ORIGINATING FROM THE PACIFIC
NORTHWEST.  BY THE END OF THE FORECAST PERIOD ON MONDAY, THE 00Z
ECMWF/UKMET HAVE TRENDED NORTHWARD CLOSER TO THE 00Z GFS, AND THE
NAM AND CMC FARTHER TO THE SOUTHWEST WITH THE SURFACE LOW.  THE
NAM IS AN OUTLIER WITH HAVING AN OVER-AMPLIFIED TROUGH OVER THE
MIDWEST, AND THE GFS IS SLIGHTLY STRONGER THAN THE MODEL
CONSENSUS.  ALTHOUGH THE UKMET AND ECMWF TRENDED CLOSER TO THE GFS
THIS CYCLE, WE WOULD LIKE TO SEE MORE MODEL CONTINUITY BEFORE
MAKING ANY MAJOR CHANGES IN THE MODEL PREFERENCE, SO THE PREVIOUS
12Z ECMWF IS PART OF THE BLEND.


PACIFIC STORM SYSTEM AFFECTING THE PACIFIC NORTHWEST THIS WEEKEND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PREFERENCE: BLEND OF THE 00Z GFS/00Z CMC/00Z GEFS MEAN
CONFIDENCE: SLIGHTLY BELOW AVERAGE

A STRONG PACIFIC STORM OFF THE PACIFIC NORTHWEST COAST ON FRIDAY
IS PROGGED TO APPROACH THIS REGION ON SATURDAY, WITH THE SURFACE
LOW EXPECTED TO REACH NORTHWESTERN WASHINGTON AROUND 00Z SUNDAY.
BOTH THE 00Z ECMWF AND UKMET ARE INDICATING TWO SEPARATE LOWS
PIVOTING AROUND EACH OTHER THROUGH THE FIRST 36 HOURS OF THE
FORECAST, WHEREAS THE OTHER MODELS ARE ON BOARD WITH THE IDEA OF
ONE MAIN SURFACE LOW.  LOOKING ALOFT, THE NAM BECOMES MORE
AMPLIFIED WITH THE SHORTWAVE AXIS BY 36 HOURS, AND THE 12Z EC MEAN
IS A BIT SLOWER THAN 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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