Prognostic Meteorological Discussion
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000
FXUS10 KWNH 201926
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
226 PM EST THU NOV 20 2014

VALID NOV 20/1200 UTC THRU NOV 24/0000 UTC

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

==============================================
12Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...STRONG SOUTHERN STREAM TROUGH LEADING TO WIDESPREAD RAIN FROM
THE PLAINS EASTWARD...

PREFERENCE: BLEND OF 12Z GFS/ECMWF
CONFIDENCE: AVERAGE

A DYNAMIC TROUGH OF SHORT TO MEDIUM WAVELENGTH WILL DIVE FROM
CALIFORNIA TOWARD THE RIO GRANDE BASIN. THE SYSTEM WILL CONTINUE
TO BE URGED ALONG TO THE EAST BY STRONG UPSTREAM FLOW...BUT THE
12Z MODELS TRENDED TOWARD A SLOWER PROGRESSION FROM LATE SATURDAY
INTO SUNDAY. THE MODELS THAT TRENDED SLOWER ARE ALSO A LITTLE
DEEPER AND FORECAST A TRACK THAT IS SUPPRESSED SOUTHWARD COMPARED
TO THE 00Z ECMWF. THESE TRENDS APPEAR REASONABLE FOR A STRONG AND
STILL DEEPENING WAVE...AND THE 12Z ECMWF SUPPORTED THE TREND. THE
NAM AND CANADIAN ARE GENERALLY CONSISTENT WITH THE GFS/ECMWF IN
THE MASS FIELDS...BUT THE NAM/CANADIAN PRECIPITATION OUTPUT IS
LESS PREFERRED. THE UKMET STRAYS FROM CONSENSUS ON DAY 3 WHEN IT
DRIVES THE CORE OF THE MID LEVEL WAVE STRONGLY EASTWARD INTO THE
DEEP SOUTH RATHER THAN LIFTING IT THROUGH THE MID MISSISSIPPI
VALLEY.


...NORTHERN STREAM TROUGH AFFECTING THE NORTHWEST/ROCKIES/NORTHERN
PLAINS...

PREFERENCE: BLEND OF THE 12Z OPERATIONAL MODELS...EXCLUDING THE
CANADIAN
CONFIDENCE: AVERAGE

THE 12Z MODELS TRENDED SLIGHTLY FASTER WITHIN THE NORTHERN STREAM
FLOW AFFECTING STATES FROM WA/OR EASTWARD TO THE DAKOTAS. STRONG
WESTERLY FLOW IN THE NORTHERN STREAM...AND CONSISTENCY IN RECENT
GEFS CYCLES LENDS SUPPORT TO THE NOTION OF A SLIGHTLY FASTER
SYSTEM. THE OLDER ECMWF AND ECMWF ENSEMBLE MEAN HAD SUGGESTED
SOMETHING A LITTLE SLOWER. THE GFS MAY ERR A BIT TOO FAR ON THE
FAST SIDE...WHICH WOULD BE CONSISTENT WITH ITS BIAS...BUT ALL OF
THIS SEEMS TO HAVE LESS OF AN IMPACT TO THE LOW LEVEL OR SURFACE
FORECAST. THE 12Z OPERATIONAL MODELS ARE CLUSTERED CLOSELY
TOGETHER...EXCEPT FOR THE CANADIAN WHICH IS LESS AMPLIFIED ALOFT
IN THE PLAINS AND FASTER AT THE SURFACE ACROSS MINNESOTA.


...PHASING RESULTING IN A DEEP CYCLONE OVER THE MIDWEST AND GREAT
LAKES BY SUN/MON...

PREFERENCE: BLEND OF 12Z NAM/GFS/ECMWF
CONFIDENCE: AVERAGE

STREAM PHASING IS FORECAST TO YIELD THE BEGINNINGS OF A VERY DEEP
MIDWESTERN U.S. CYCLONE BY SUNDAY. OVER SEVERAL MODEL CYCLES THE
ENSEMBLE MEANS HAVE BEEN CONSISTENT IN THE PLACEMENT AND INTENSITY
OF THE SURFACE LOW. THE 12Z CYCLE TRENDED EASTWARD...WHICH IS
CONSISTENT WITH TRENDS OF A MORE SUPPRESSED SOUTHERN STREAM WAVE
AND QUICKER NORTHERN STREAM WAVE. THE 12Z GEFS MEAN SUPPORTS THIS
TREND FROM THE OPERATIONAL MODELS...INCLUDING THE ECMWF. THE NAM
IS LIKELY NOT QUITE DEEP ENOUGH WITH THE SURFACE LOW...WHICH MOST
GUIDANCE HAS DROPPING BELOW 990 MB BY 24/00Z.


...NORTHEASTERN U.S...

PREFERENCE: ANY OF THE OPERATIONAL MODELS
CONFIDENCE: HIGH

A SHORTWAVE TROUGH WILL SWING THROUGH NEW ENGLAND BY
FRIDAY...FOLLOWED BY WARM ADVECTION AND A TRANSITION TOWARD MILD
AIR AND SOUTHWESTERLY FLOW ALOFT. THE MODELS HANDLE THIS SIMILARLY.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

BURKE
$$




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