Prognostic Meteorological Discussion
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000
FXUS10 KWNH 221902
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
301 PM EDT FRI MAY 22 2015

VALID MAY 22/1200 UTC THRU MAY 26/0000 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.


SYSTEM MOVING FROM THE SOUTHWEST INTO NRN HIGH PLAINS SUN/MON
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY DAY 1-2 PREFERENCE: BLEND OF 12Z OPERATIONAL MODELS
PRELIMINARY DAY 3 PREFERENCE: BLEND OF 00Z ECMWF ENSEMBLE MEAN/12Z
GEFS MEAN
CONFIDENCE: AVERAGE

A LARGE BROAD TROF EXISTS OVER THE WEST WITH THREE FOCI ROTATING
AROUND THE CENTROID NEAR SE ID/N UT. THE INITIAL AND LARGEST WAVE
EJECTS INTO THE GREAT PLAINS SUNDAY INTO MONDAY. MULTIPLE RUNS OF
THE NAM AND GFS ARE CONSISTENTLY LEFT OF CONSENSUS WITH THE
SURFACE LOW TRACK. THEY ARE STRONGER AND FURTHER NORTH OWING TO
EMPHASIS ON ENERGY ALOFT EJECTING FROM THE BASE OF THE TROUGH
TOWARD THE NORTHERN PLAINS. THE ECMWF HAS BEEN CONSISTENTLY MORE
SUPPRESSED OR TO THE SOUTH AND EAST OF CONSENSUS...BUT THE THE 12Z
ECMWF TRENDED TOWARD THE NORTH. OVERALL...THE WEIGHT OF THE
MULTI-ENSEMBLE CONSENSUS SHIFTED CLOSER TO THE 12Z GEFS MEAN
SOLUTION. GOOD AGREEMENT OCCURS WITH THE 12Z OPERATIONAL MODELS
THROUGH DAY 2...BUT A GOOD AMOUNT OF SPREAD STILL EXISTS IN THE
DAY 3 SOLUTION. EVEN THOUGH THE 12Z ECMWF HAS SHIFTED NORTH IT
REMAINS SUPPRESSED. WITH CONTINUED SPREAD AT DAY 3 WE CONTINUED A
DAY 3 PREFERENCE OF BLEND OF ENSEMBLE MEANS...12Z GEFS/00Z ECMWF
ENSEMBLE MEAN.


SYSTEM ALONG WEST COAST INTO AZ/NM BY MONDAY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: BLEND OF 12Z NAM/GFS/CMC
CONFIDENCE: ABOVE AVERAGE

A SECOND WAVE DROPS DOWN THE WESTERN SIDE OF THE TROF SATURDAY
NIGHT INTO THE BASE BY THE END OF THE PERIOD... MOST GUIDANCE IS
IN QUITE GOOD AGREEMENT IN THE EVOLUTION PARTICULARLY UNTIL EARLY
MONDAY.  SOME SUBTLE DISAGREEMENT STARTS ON MONDAY WHEN AS THE 12Z
NAM/GFS/CMC APPEAR A BIT MORE AMPLIFIED. THE 00Z ECMWF WAS A BIT
DAMPENED.  THE 12Z ECMWF WAS QUITE DIFFERENT WITH ITS SOLUTION
COMPARED TO ITS PRIOR RUNS AND HAD A DEEPER SOLUTION WHICH
EVENTUALLY OUTPACES THE OTHER 12Z OPERATIONAL GUIDANCE...AND AS
SUCH IS GIVEN LESS WEIGHT. THE 12Z UKMET WAS ALSO AN OUTLIER BUT
FOR THE OPPOSITE REASON BEING WEAKER/FLATTER.


SYSTEM DEVELOPING ALONG THE PACIFIC NORTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PRELIMINARY PREFERENCE: NON-UKMET BLEND
CONFIDENCE: ABOVE AVERAGE

UPSTREAM ENERGY BREAKS THROUGH THE NARROWING RIDGE ACROSS
NORTHWEST CANADA AND DEVELOPS THE CANADIAN PACIFIC TROF INTO A
BETTER DEFINED LOW OVER THE NORTHWEST U.S. BY DAY 3.  VERY GOOD
AGREEMENT OF THIS SOLUTION IN TIMING AND INTENSITY EXCEPT FOR THE
12Z UKMET.  12Z NAM IS ALSO A BIT PROGRESSIVE TOWARD THE END OF
THE PERIOD BUT STILL REMAINS A VIABLE SOLUTION.

...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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