Prognostic Meteorological Discussion
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FXUS10 KWNH 281655
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1155 AM 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 NAM/GFS EVALUATION AND PRELIMINARY 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
SOUTHERN STREAM CA PREFERENCE: BLEND OF 00Z ECMWF/UKMET/CANADIAN

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 INDICATE WHAT SEEMS TO BE A REALISTICALLY
SLOWER PROGRESSION AS THE SHORTWAVE DIGS TOWARD THE NORTHWEST U.S.
THIS WOULD SEEM TO BE A LEGITIMATE TREND.

CONFIDENCE IS LOWERED...HOWEVER...BECAUSE OUR PREFERENCE FOR THE
SOUTHERN STREAM IS OPPOSITE OF THAT FOR THE NORTHERN STREAM. GIVEN
UPSTREAM RIDGE AMPLIFICATION AND A VIGOROUS SHORTWAVE TROUGH
DIVING ALONG 145 DEGREES WEST...THE GFS/NAM SOLUTIONS DO NOT
APPEAR DEEP OR SLOW ENOUGH OFF OF CALIFORNIA. IN THE LONG
RUN...THE SPREAD IS NARROWING...ESPECIALLY AS THE ECMWF ADJUSTS
AWAY FROM SOME OF ITS VERY SLOW SOLUTIONS OF THE PAST FEW DAYS.
STILL...THE ECMWF ENSEMBLE MEAN IS PREFERRED OVER THE GEFS IN BOTH
THE SHORT AND MEDIUM RANGE FORECASTS...AND THE OPERATIONAL MODELS
BEST SUPPORTED BY THE ECMWF MEAN ARE AND HAVE BEEN THE
ECMWF/UKMET/CANADIAN.


SHORTWAVE MOVING THROUGH THE NORTHWEST/NRN PLAINS
ARCTIC FRONT SWEEPING THROUGH THE CENTRAL/EASTERN U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 12Z NAM WITH 00Z ECMWF/UKMET

MODELS ARE SIMILAR AS A BROAD TROUGH AND SHARPLY DEFINED COLD
FRONT SWEEP ACROSS MUCH OF THE U.S. THE MAIN DIFFERENCE IS
TIMING...WITH THE 00Z CANADIAN BEING SLOW...AND RECENT GFS RUNS
BEING ON THE FAST SIDE. THE REMAINING MODELS CLUSTER NICELY AND
HAVE SUPPORT FROM THE ECMWF ENSEMBLE MEAN.


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

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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