Prognostic Meteorological Discussion
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FXUS10 KWNH 261651
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1250 PM EDT SUN APR 26 2015

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

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

12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


DEEP TROUGH/CLOSED LOW CURRENTLY OVER THE SOUTHWEST U.S.
LOW PRESSURE DEVELOPING OVER THE SOUTHERN PLAINS BY MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 00Z ECMWF / 00Z ECMWF MEAN BLEND
            NEXT CLOSEST MODEL IS THE 00Z CMC
CONFIDENCE: AVERAGE

THE 12Z GFS APPEARS TO BE ON THE STRONGER SIDE OF THE
DETERMINISTIC MODELS AND ALSO A BIT NORTH OF THE CONSENSUS TOWARD
THE END OF THE DAY ON MON...WHERE THE 00Z ECMWF AND 12Z NAM SHOW
GOOD AGREEMENT WITH THE ENSEMBLE MEANS. THE 12Z NAM HOWEVER...GOES
ASTRAY ON TUE WITH TAKING THE UPPER TROUGH QUICKER TO THE EAST
THAN MOST OF THE DETERMINISTIC/ENSEMBLE GUIDANCE. THE 00Z UKMET IS
ON THE SLOW SIDE AND ALSO WEAKER WITH THE CORE OF THE UPPER LOW.
THE 00Z CMC IS THE CLOSEST DETERMINISTIC MODEL AT THIS TIME TO THE
PREFERRED 00Z ECMWF AND THE 00Z ECMWF MEAN.


DEEP CLOSED LOW REMAINING ACROSS NEW ENGLAND
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

THE MODELS SHOW SIMILARLY WITH THIS SYSTEM.


TROUGH/FRONT CROSSING THE NORTHERN PLAINS/UPPER MIDWEST THROUGH TUE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE...THROUGH 48 HOURS
            BLEND OF THE 00Z GFS/00Z UKMET...AFTER 48 HOURS
CONFIDENCE: AVERAGE

WITH THE EXCEPTION OF THE 00Z UKMET...MODEL TRENDS HAVE BEEN TO
SLOW THE BASE OF THE UPPER TROUGH MOVING THROUGH THE NRN PLAINS
MON/TUE...AND THERE IS NOW A CONSENSUS TO HAVE A PIECE OF
MID-LEVEL VORTICITY TO BREAK OFF AND DROP SWD INTO THE CNTRL
MISSOURI RIVER VALLEY BY WED MORNING. THE 12Z GFS...00Z ECMWF AND
00Z CMC SHOW GOOD AGREEMENT WITH THE 00Z ECMWF/06Z GEFS MEAN
HERE...SUGGESTING THE 00Z UKMET TO BE AN OUTLIER AND THE 12Z NAM
TO BE TOWARD THE WEAK SIDE OF THE MODEL CLUSTERING.


UPPER TROUGHING OVER THE PACIFIC NORTHWEST TUE/WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z GFS BLEND
CONFIDENCE: ABOVE AVERAGE

THE LATEST DETERMINISTIC GUIDANCE SHOWS GOOD AGREEMENT THROUGH
F060 HOURS WITH A SHORTWAVE AND COLD FRONT REACHING THE PACIFIC
NORTHWEST. A SECOND SHORTWAVE IS EXPECTED TO DROP TOWARD THE
PACIFIC NORTHWEST COAST BY WED EVENING WITH THE 12Z GFS SHOWING
THE WEAKEST OF THE DETERMINISTIC GUIDANCE...AND ALSO FASTER. GIVEN
THE GOOD CLUSTERING OUTSIDE OF THE 12Z GFS...A NON 12Z GFS BLEND
IS PREFERRED.


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

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

OTTO

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