Prognostic Meteorological Discussion
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FXUS10 KWNH 181917
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
317 PM EDT THU SEP 18 2014

VALID SEP 18/1200 UTC THRU SEP 22/0000 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.
==============================================

...REMNANTS OF ODILE...

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

THE 12Z CANADIAN STRAYS FAR FROM CONSENSUS WITH RESPECT TO QPF.
THE NAM/GFS/ECMWF APPEAR CONSISTENT WITH ONE ANOTHER. VIEWING THE
FULL 12Z SUITE...THE UKMET WAS SIMILAR ENOUGH IN THE MID LEVEL
MASS FIELDS AND IN QPF...TO INCLUDE IN OUR PREFERENCE.


...DEEP UPPER TROUGH/CLOSED LOW AFFECTING THE WESTERN STATES
THROUGH SAT...

PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET/CANADIAN
CONFIDENCE: ABOVE AVERAGE

FEW MODEL DIFFERENCES EXIST HERE. THE MOST NOTICEABLE EXCEPTION IS
THE 12Z NAM...WHICH IS MUCH SLOWER TO BRING A SHORTWAVE AROUND THE
BASE OF THE LOW AND SWING THE LARGER SCALE LOW INTO A NEGATIVE
TILT AROUND 21/00Z. THE GLOBAL MODELS...HOWEVER...SHOW STRONG
AGREEMENT.


...UPPER TROUGH DIGGING INTO THE EASTERN U.S THIS WEEKEND...
...SURFACE LOW DEVELOPING OFF THE SOUTHEAST UNITED STATES COAST
FRI/SAT...

PREFERENCE: BLEND OF 12Z GEFS MEAN WITH 12Z ECMWF
CONFIDENCE: AVERAGE

A NUMBER OF PIECES OF GUIDANCE...ESPECIALLY THE GFS AND
UKMET...HAVE TRENDED FASTER WITH A NORTHERN STREAM TROUGH DIGGING
INTO THE MIDWEST/GREAT LAKES. THE 12Z GFS MAY DO SO A LITTLE TOO
AGGRESSIVELY...AND ITS SURFACE LOW POSITION OVER SOUTHERN QUEBEC
AT 22/00Z HAS RELATIVELY LITTLE SUPPORT. IT APPEARS THE 12Z GEFS
MEAN DOES A GOOD JOB OF DISPLAYING THE TREND WHILE DEPICTING A
BETTER SUPPORTED SURFACE PATTERN...BOTH IN QUEBEC AND OFF THE
SOUTHERN ATLANTIC COAST. THE ECMWF TRENDED SLOWER OFF THE ATLANTIC
COAST...BUT WE ARE STILL COMFORTABLE BLENDING THE GEFS MEAN WITH
THE 12Z ECMWF TO REPRESENT WPC CONTINUITY WITH A NUDGE TOWARD
TRENDS.


...LEAD SHORTWAVE INTO THE PACIFIC NORTHWEST THIS WEEKEND...

PREFERENCE: BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

A DEEP LONGWAVE TROUGH OFFSHORE SHOULD HAVE LITTLE IMPACT THROUGH
SUNDAY...BUT MODELS DO BRUSH THE PACIFIC NW COAST WITH LOW
PRESSURE ASSOCIATED WITH A LEAD SHORTWAVE THIS WEEKEND.

...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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