Prognostic Meteorological Discussion
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FXUS10 KWNH 281911
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
210 PM EST FRI NOV 28 2014

VALID NOV 28/1200 UTC THRU DEC 02/0000 UTC

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

DAY 3 / SUN NIGHT AND MON IN THE WEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NORTHERN STREAM OR/WA PREFERENCE: BLEND OF 12Z NAM/GFS/CANADIAN
SOUTHERN STREAM CA PREFERENCE: BLEND OF 12Z NAM/ECMWF/CANADIAN

CONFIDENCE: AVERAGE

AFTER BEING A BIT OVERZEALOUS WITH THE SPEED AND DEPTH OF THE
NORTHERN STREAM...THE ECMWF ENSEMBLE MEAN SOLUTIONS HAVE TRENDED
SLOWER WITH A DAY 3 SHORTWAVE IMPACTING THE PACIFIC NORTHWEST.
MORE RECENT RUNS OF THE OPERATIONAL ECMWF...NAM...AND GFS HAVE
DEPICTED A SHARPER SHORTWAVE...AS OFTEN HAPPENS WHEN WE GET CLOSER
IN TIME. THE 12Z NAM/GFS INDICATED A REALISTICALLY SLOWER
PROGRESSION AS THE SHORTWAVE DIGS TOWARD THE NORTHWEST U.S...AND
THIS TREND WAS BACKED UP BY THE CANADIAN AND ECMWF...ALTHOUGH THE
ECMWF STILL APPEARS SOMEWHAT FAST BY DAY 3.

IN THE SOUTHERN STREAM...GIVEN UPSTREAM RIDGE AMPLIFICATION AND A
VIGOROUS SHORTWAVE TROUGH DIVING ALONG 145 DEGREES WEST...SLOWER
AND DEEPER SOLUTIONS ARE PREFERRED. THAT BEING SAID...THE MODEL
SPREAD HAS NARROWED...ESPECIALLY AS THE ECMWF CONTINUES TO ADJUST
AWAY FROM SOME OF ITS VERY SLOW SOLUTIONS OF THE PAST FEW DAYS.
THE GFS/NAM ARE STILL SOME OF THE FASTER SOLUTIONS...BUT THE NAM
IS REASONABLY SIMILAR TO THE GROWING ENSEMBLE CONSENSUS AND THE
12Z ECMWF/CANADIAN. THE UKMET WAS THE ONLY MODEL THAT DID NOT
TREND TOWARD THE NEW CONSENSUS SOLUTION...CAUSING IT TO GO OUT OF
PHASE BY DAY 3 IN BOTH NORTHERN AND SOUTHERN STREAMS.


SHORTWAVE MOVING THROUGH THE NORTHWEST/NRN PLAINS
ARCTIC FRONT SWEEPING THROUGH THE CENTRAL/EASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE
CANADIAN
CONFIDENCE: ABOVE AVERAGE

MODELS ARE SIMILAR AS A BROAD TROUGH AND SHARPLY DEFINED COLD
FRONT SWEEP ACROSS MUCH OF THE U.S. THE MAIN DIFFERENCE HAS BEEN
TIMING...WITH THE CANADIAN BEING SLOW...AND CERTAIN RUNS OF THE
GFS BEING ON THE FAST SIDE. DURING THE 12Z CYCLE MOST MODELS
TRENDED SLIGHTLY FASTER IN MOVING THIS WEATHER SYSTEM THROUGH THE
GREAT LAKES...OHIO VALLEY...AND NORTHEAST U.S. THIS BRINGS THEM
CLOSER TO THE GFS...ALLOWING US TO RECOMMEND A NON-CANADIAN BLEND.


SHORTWAVE APPROACHING CALIFORNIA SUNDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE GFS
CONFIDENCE: ABOVE AVERAGE

MODELS INDICATE SIMILAR TIMING AND DEPTH FOR THIS LOW
AMPLITUDE...LEAD SHORTWAVE...WHICH ARRIVES ON THE CENTRAL
CALIFORNIA COAST SUNDAY. THE NAM IS ONE OF THE DEEPER
SOLUTIONS...BUT THIS DOES NOT APPEAR TO FACTOR INTO ITS
PRECIPITATION FORECAST. ONLY THE GFS APPEARED TO BE LESS
DESIRABLE...WITH A SOMEWHAT WEAKER TROUGH AND THEN RAPID
TRANSITION TO SHORTWAVE RIDGING. THIS LIKELY CONTRIBUTES TO WHAT
LOOKS LIKE A DRIER FORECAST FROM THE GFS COMPARED TO 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...

BURKE
$$




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