Prognostic Meteorological Discussion
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FXUS10 KWNH 261624
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1124 AM EST FRI DEC 26 2014

VALID DEC 26/1200 UTC THRU DEC 30/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS


...SHORTWAVE LIFTING FROM THE CENTRAL PLAINS TO THE UPPER
MIDWEST...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: ABOVE AVERAGE

THE 12Z NAM IS A TAD STRONGER AND SLOWER THAN THE MULTI-MODEL
CONSENSUS WITH THE SHORTWAVE AND ASSOCIATED SURFACE LOW LIFTING
NORTHEAST ACROSS THE MIDWEST AND UPPER GREAT LAKES REGION THROUGH
EARLY SAT. THE REMAINING MODELS ARE REASONABLY WELL CLUSTERED WITH
TIMING AND DEPTH...SO WILL PREFER A NON-NAM CONSENSUS.


...SHORTWAVE ENERGY SHEARING OVER THE FOUR CORNERS/SOUTHERN
PLAINS/SOUTHEAST...

PREFERENCE: 12Z GFS
CONFIDENCE: AVERAGE

SHORTWAVE ENERGY LEFT BEHIND OVER THE FOUR CORNERS REGION BY LATE
SAT WILL SHEAR EAST OUT ACROSS THE SOUTHERN PLAINS ON SUN. THE 12Z
NAM/00Z UKMET AND 00Z GEM ARE A BIT SLOWER THAN THE 00Z ECMWF AND
12Z GFS. BY LATER SUN AND MON...THE 00Z ECMWF BECOMES THE SOLN
THAT HANGS ON TO A RELATIVELY STRONGER SHORTWAVE THAT CROSSES THE
SOUTHEAST...AND AS A RESULT THE ECMWF HAS A STRONGER SFC LOW THAT
DEVELOPS ALONG THE TAIL END OF A FRONT. ALL OF THE MODELS DO
INDICATE A WAVE DEVELOPING DESPITE THE SHEARING OUT OF SHORTWAVE
ENERGY...BUT THE PREFERENCE WILL BE FOR A RELATIVELY MODEST WAVE
AS COMPARED TO THE ECMWF. THE 06Z GEFS MEAN AND 00Z ECENS MEAN
FAVOR A RELATIVELY FLATTER WAVE TOWARD THE 12Z GFS SOLN. WILL
THEREFORE PREFER THE 12Z GFS.


...STRONG SHORTWAVE REACHING THE PACIFIC NORTHWEST BY LATE
SATURDAY...
...DEEP TROUGH EVOLVING OVER THE WESTERN U.S BY SUNDAY/MONDAY....

PREFERENCE: BLEND OF THE 00Z ECMWF AND 00Z GEM
CONFIDENCE: SLIGHTLY BELOW AVERAGE

MODELS SHOW A STOUT UPPER RIDGE SETTING UP ACROSS THE EASTERN
PACIFIC AT THE START OF THE PERIOD. ON SAT...A PRONOUNCED
SHORTWAVE IS FORECAST TO DIG SOUTHWARD FROM THE GULF OF AK
CARRYING STRONG HEIGHT FALLS INTO THE STATE OF WA BY SAT EVENING.
THIS ENERGY WILL TRAVERSE THE INTERMOUNTAIN REGION THROUGH
MON...WITH SOME OF IT SHEARING OUT INTO THE PLAINS BY LATE MON.
HOWEVER...ALL OF THE MODELS SHOW A DEEP TROUGH IMPACTING MOST OF
THE GREAT BASIN BY MON. THE 12Z NAM OVERALL HAS A TENDENCY TO BE
TOO STRONG WITH THE ENERGY COMPARED TO THE MULTI-MODEL CONSENSUS.
BY THE END OF THE PERIOD...THE NAM FAVORS A STRONGER CLOSED LOW
OVER THE GREAT BASIN WHEREAS THE GLOBAL MODELS ARE WEAKER WITH THE
DEPTH OF THE TROUGH AND ANY CLOSED OFF FEATURE. THE 12Z GFS AND
00Z UKMET TENDED TO BE RELATIVELY WEAKER WITH THE HEIGHT FALLS
OVERALL. THE 00Z ECMWF AND 00Z GEM SPLIT THE DIFF. THE 06Z GEFS
MEAN DOES FAVOR A MODESTLY WEAKER SOLN LIKE THE GFS/UKMET...BUT
THE ECENS MEAN FAVORS THE MODESTLY DEEPER ECMWF/GEM CAMP. THE NAM
IS ON ITS OWN AT THE END OF THE PERIOD IN BEING TOO DEEP. WILL
PREFER A BLEND OF THE 00Z ECMWF AND 00Z GEM FOR THE TIME BEING.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

ORRISON

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