Prognostic Meteorological Discussion
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FXUS10 KWNH 241709
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
108 PM EDT SUN MAY 24 2015

VALID MAY 24/1200 UTC THRU MAY 28/0000 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.


SHORTWAVE LIFTING FROM GREAT PLAINS INTO GREAT LAKES BY MONDAY
NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PRELIMINARY PREFERENCE: BLEND OF 12Z GFS/00Z ECMWF/00Z UKMET
CONFIDENCE: ABOVE AVERAGE

SHORTWAVE MOVING OUT OF NORTH TEXAS WILL LIFT INTO THE WESTERN
GREAT LAKES AND SHEAR OUT INTO THE POLAR STREAM BY TUESDAY
MORNING.  GOOD CLUSTERING EXISTS BETWEEN THE 12Z GFS/00Z UKMET/00Z
ECMWF AND ARE GOOD REPRESENTATIVES WITHIN THE ENSEMBLE SPREAD AND
ECMWF MEANS.  THE CMC LAGS AND OVER-STREGTHENS THE SURFACE LOW
SENDING IT FURTHER NORTH AND WEST. THE 12Z NAM APPEARS TO START
OFF STRONGER AND SOUTHEAST OF THE GUIDANCE.  IT REMAINS AN EASTERN
SOLUTION THROUGHOUT THE EVOLUTION OF THE LOW AS IT ENTERS CANADA
BY MONDAY NIGHT/TUESDAY MORNING.  IT REMAINS PLAUSIBLE BUT GIVEN
THE PACKING OF THE OTHER OPERATIONAL AND ENSEMBLE GUIDANCE...IT
SHOULD BE USED WITH SOME TREPIDATION.


CALIFORNIA SHORTWAVE EJECTING INTO THE GREAT PLAINS BY MONDAY
NIGHT/TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 12Z GFS WITH 06Z GEFS MEAN/00Z
ECMWF ENSEMBLE MEAN
CONFIDENCE: AVERAGE

A SHORTWAVE CURRENTLY OVER CALIFORNIA ROUNDS THE BASE AND COMBINED
WITH THE MEAN LARGE SCALE TROF EJECTS INTO THE GREAT PLAINS
DEVELOPING A LARGE AREA OF LOWER SURFACE PRESSURES WITH BROAD A
SURFACE LOW DEVELOPING. THE 12Z GFS ALONG WITH 06Z GEFS MEAN AND
00Z ECMWF HAVE A BROADER LOW PRESSURE WITH A WEAKER WAVE LIFTING
FROM SOUTHEAST COLORADO TO THE WESTERN GREAT LAKES BY THE END OF
THE PERIOD. THE 00Z ECMWF AND 00Z UKMET EJECT MORE ENERGY WITH THE
SOUTHERN SHORTWAVE AND DEVELOP A STRONGER SURFACE LOW THAT MOVES
FROM SOUTH TEXAS TO THE WESTERN GREAT LAKES BY THE END OF THE
PERIOD. THE STRENGTH OF THE LOW AND DISCONTINUITY WITH THE 23/12Z
ECMWF AND THE 00Z ECMWF MEAN PROVIDES MORE CONFIDENCE IN A 12Z
GFS/06Z GEFS MEAN/00Z ECMWF ENSEMBLE MEAN BLEND.


NORTHWEST U.S. CUT OFF LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: NON-CMC BLEND
CONFIDENCE: ABOVE AVERAGE

THE CUTOFF TROF OVER SOUTHWEST BRITISH COLUMBIA SLOWLY DROPS INTO
THE PACIFIC NORTHWEST AND BEGINS TO DEVOLVE INTO THE NORTHERN
STREAM IN ADVANCE OF A MUCH STRONGER UPPER LOW UPSTREAM BY THE END
OF THE PERIOD.  VERY GOOD AGREEMENT BETWEEN THE OPERATIONAL AND
ENSEMBLE GUIDANCE PROVIDES GOOD CONFIDENCE THROUGH DAY TWO. DAY
THREE ONLY THE CANADIAN GETS OUT OF PHASE WITH THE OTHER GUIDANCE
BECOMING SLIGHTLY FASTER TOWARD THE SOUTHEAST AND IS NOT SUPPORTED
IN THE PREFERENCE.

...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
$$




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