Prognostic Meteorological Discussion
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FXUS10 KWNH 181753
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
149 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 NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES
==================================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==================================================

...REMNANTS OF ODILE...

PREFERENCE: BLEND OF 12Z NAM/GFS WITH 00Z ECMWF

THE 12Z UKMET LEANS FORWARD WITH THE TROUGH AXIS OVER TEXAS. THE
12Z CANADIAN STRAYS FAR FROM CONSENSUS WITH RESPECT TO QPF. THE
NAM/GFS/ECMWF APPEAR CONSISTENT WITH ONE ANOTHER.


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

PREFERENCE: BLEND OF THE 12Z GFS/UKMET/CANADIAN WITH 00Z ECMWF

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 NEAR SOUTHERN CALIFORNIA...AND SWINGING 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 00Z ECMWF

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. BLENDING THE GEFS MEAN WITH THE 00Z ECMWF
SHOULD REPRESENT WPC CONTINUITY WITH A NUDGE TOWARD TRENDS.


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

PREFERENCE: BLEND OF THE OPERATIONAL MODELS

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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