Prognostic Meteorological Discussion
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000
FXUS10 KWNH 211632
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1231 PM EDT THU MAY 21 2015

VALID MAY 21/1200 UTC THRU MAY 25/0000 UTC

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

12Z MODEL EVALUATION WITH PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT
RANGE FORECASTS.


SOUTHWEST U.S. TROF LIFTING INTO FRONT RANGE
~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND 00Z ECMWF/ECMWF ENSEMBLE MEAN

MODELS AGREE THAT A BROAD LOW OVER WEST COAST WILL DIG CENTERING
OVER LAS VEGAS BY EARLY SATURDAY.  SOLUTIONS BEGIN TO DIVERGE IN
TIMING AND STRENGTH WITH THE EJECTION TO THE PLAINS...
PARTICULARLY IN THE SURFACE PATTERN.  THE NCEP MODELS HAVE BEEN
TENDING TO DEVELOP A MORE AGGRESSIVE AND FASTER SURFACE LOW IN
NORTHEASTERN COLORADO WITH INVERTED SURFACE TROF ACROSS THE
NORTHERN PLAINS WHILE THE 00Z ECMWF TENDS TO HOLD BACK THE ENERGY
IN THE BASE...CURRENT PREFERENCE IS TIED TO THE ECWMF WITH ITS
BETTER RUN TO RUN CONSISTENCY.  THE 12Z NAM APPEARS TO BE GETTING
IN BETTER AGREEMENT WITH A VIABLE SURFACE SOLUTION BY END OF THE
PERIOD BUT WAS A BIT INCONSISTENT WITH THE INITIAL EJECTING
SHORTWAVE WITH A DEEPER FURTHER NORTH SOLUTION. THE 12Z GFS
CONTINUES TO BE CONSISTENT WITH ITS PRIOR RUNS AND LOOKS
REASONABLE UP TO DAY TWO. HOWEVER IT THEN BREAKS WITH THE
PREFERRED SURFACE SOLUTION OF THE 00Z ECMWF/ECMWF ENSEMBLE MEAN.

LOOSELY DEFINED TROF OVER NORTHWEST U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 00Z ECMWF/ECMWF ENSEMBLE MEAN

LARGE MODEL AND ENSEMBLE SOLUTION SPREAD EXISTS WITH A LOOSELY
DEFINED TROF ACROSS COASTAL BRITISH COLUMBIA. THE EVOLUTION OF
THIS FEATURE IS HIGHLY TIED TO THE UPSTREAM TROF DEVELOPING OVER
THE GULF OF ALASKA. THE GFS/GEFS MEAN CONTINUE TO BE
STRONGEST/FASTEST TO PULL ENERGY SOUTHWARD INTO OREGON AND
CALIFORNIA BY THE END OF THE PERIOD...WHILE ECMWF SOLUTIONS HAVE
BEEN LESS AGGRESSIVE...INFLUENCED BY THE SLOWER BUT ALSO MORE
CONSISTENT RUN TO RUN UPSTREAM EVOLUTION.  THE ECMWF EVENTUALLY
KICKS THE TROF SOUTHWARD BY DAY 3 WHICH IS IN AGREEMENT WITH WPC
MEDIUM-RANGE DISCUSSION...PMDEPD. GIVEN HIGH SPREAD CONFIDENCE IS
QUITE LOW.


SYSTEMS MOVING THROUGH THE NORTHEAST/MID-ATLANTIC
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF GENERAL MODEL GUIDANCE

LEADING WEAK SHORTWAVE ACROSS THE EASTERN GREAT LAKES ALONG WITH
DEEPENING LARGE SCALE TROF ACROSS JAMES BAY INTO QUEBEC CONTINUE
TO FOLLOW MODEL TRENDS AND REMAIN IN EXCELLENT AGREEMENT.  THE
SURFACE REFLECTIONS IN THE CAROLINA/COASTAL ATLANTIC AS WELL AS
THE NEW ENGLAND LOW AND COLD FRONT ALSO SHOWS GOOD AGREEMENT
BEFORE EXITING THE U.S. BY MIDDAY SATURDAY.


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

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

GALLINA/BURKE
$$





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