Prognostic Meteorological Discussion
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000
FXUS10 KWNH 241859
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~
PREFERENCE: BLEND OF 12Z OPERATIONAL MODELS
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. THE 12Z NAM STARTED A TREND OF SUBTLE EASTWARD SHIFT IN
THE GUIDANCE.  THE 12Z ECMWF/12Z CMC/12 UKMET HAVE COME INTO
BETTER AGREEMENT AND FURTHER EAST WITH THE SURFACE LOW TOWARD
MONDAY NIGHT/TUESDAY MORNING.  THIS NOW PLACES THE 12Z GFS AS THE
WESTERN MEMBER OF THE CLUSTER.  THOUGH THE 12Z UKMET DOES HAS A
SECONDARY SURFACE RESPONSE TOWARD A DEEPER UPPER LEVEL SOLUTION
FROM THE NORTHERN STREAM.  BETTER AGREEMENT OF ALL OF THE 12Z
OPERATIONAL GUIDANCE FITS IN WELL WITH THE EARLIER PREFERENCE AND
00Z ENSEMBLE MEMBERS PROVIDING MUCH BETTER CONFIDENCE IN SOLUTION.



CALIFORNIA SHORTWAVE EJECTING INTO THE GREAT PLAINS BY MONDAY
NIGHT/TUESDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~
PREFERENCE: BLEND OF 12Z GFS/12Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

A SHORTWAVE CURRENTLY OVER CALIFORNIA ROUNDS THE BASE AND COMBINED
WITH THE MEAN LARGE SCALE TROF EJECTS INTO THE GREAT PLAINS
DEVELOPING A BROADE AREA OF LOWER SURFACE PRESSURES. THE 12Z GFS
ALONG WITH 06Z GEFS MEAN AND 00Z ECMWF HAVE A BROADER LOW PRESSURE
ZONE ACROSS THE PLAINS WITH A WEAKER SURFACE WAVE LIFTING FROM
SOUTHEAST COLORADO TO THE WESTERN GREAT LAKES BY THE END OF THE
PERIOD. THE 00Z ECMWF AND 00Z UKMET EJECTED 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.  THIS TREND WAS CONTINUED BY THE 12Z UKMET BUT THE 12Z
ECMWF LOOKS MUCH MORE IN AGREEMENT WITH ORIGINAL PREFERENCES OF
THE 12Z GFS AND 06Z GEFS MEAN/00Z ECMWF ENSEMBLE MEAN BLEND...AND
SO IS NOW INCLUDED IN THE PREFERENCE WHICH ALSO PROVIDES A BIT
MORE CONFIDENCE.


NORTHWEST U.S. CUT OFF LOW
~~~~~~~~~~~~~~~~~~~~~~~~~~
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. THE
DISCREPANCIES WITH THE 00Z CMC REMAIN WITH THE 12Z RUN...THOUGH
LESSER SO. THE UPPER LEVEL PATTERN REMAINS A BIT DEEPER AND
SOUTHEAST OF THE OTHER GUIDANCE. SUBTLE BUT SIGNIFICANT
DIFFERENCES OCCUR AT THE SURFACE COMPARED TO THE OTHER OPERATIONAL
MODELS.  THE 12Z CANADIAN IS VERY BROAD AND WEAK WHILE THE OTHER
OPERATIONAL GUIDANCE FAVOR DEVELOPING A BETTER ORGANIZED SURFACE
LOW IN NORTHEAST WY AT THE END OF THE PERIOD.

...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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