Prognostic Meteorological Discussion
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000
FXUS10 KWNH 310641
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
240 AM EDT MON AUG 31 2015

VALID AUG 31/0000 UTC THRU SEP 03/1200 UTC

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

00Z NAM/GFS EVALUATION INCLUDING THE UKMET/CANADIAN/ECMWF AND
PREFERENCES

UPPER TROUGH FORMING OVER THE PACIFIC NORTHWEST TUE-WED...

PREFERENCE: MODEL CONSENSUS OR ENSEMBLE MEANS
CONFIDENCE: AVERAGE

USUAL DIFFERENCES WITH THE INTENSITY AND SPEED OF SHORTWAVE
TROUGHS EMBEDDED WITHIN THE LONGER WAVE TROUGH CREATE SUFFICIENT
UNCERTAINTY WITH ITS STRUCTURE TO SUPPORT A CONSENSUS OR ENSEMBLE
MEAN APPROACH UNTIL THE TROUGH MOVES CLOSER TO THE SHORE...WITH
THE NAM/GFS A LITTLE FASTER THAN THE 12Z ECMWF.

SHORTWAVE TROUGHS EXTENDING FROM THE OH VALLEY INTO TEXAS...

PREFERENCE: GFS
CONFIDENCE: AVERAGE

THE NAM AND GFS REMAIN CLOSE IN POSITION AND STRENGTH ACROSS THE
OH VALLEY AND ALSO ACROSS TEXAS THROUGH THE PERIOD...WITH THE
ECMWF TRENDING SLOWER ACROSS THE OH VALLEY BUT STILL NEAR THE FAST
SIDE OF THE GUIDANCE...AND ALSO TRENDING WEAKER ACROSS TEXAS.
GIVEN THESE TRENDS...THE ECMWF APPEARS TO BE SUPPORTING EARLIER
PREFERENCES OF THE GFS.

UPPER LOW OVER THE WESTERN CAROLINAS...

PREFERENCE: 1/2 EACH NAM/ECMWF
CONFIDENCE: ABOVE AVERAGE

ALTHOUGH SLIGHT DIFFERENCES REMAIN...THE 00Z GUIDANCE HAS
CONVERGED UPON A COMMON SOLUTION...WITH THE THE HIGHEST RESOLVING
GUIDANCE INCLUDING THE NAM AND ECMWF LIKELY PROVIDING THE MOST
USEFUL AND DETAILED INFORMATION.  REFER TO THE QPFPFD FOR MORE
INFORMATION ON RAINFALL.

REMNANTS OF ERIKA...

PREFERENCE: GFS
CONFIDENCE: AVERAGE

THE GFS APPEARS CLOSEST TO THE REMNANT POSITION AND STRENGTH OF
ERIKA...WITH THE NAM/ECMWF SIMILAR IN POSITION BUT POSSIBLY TOO
STRONG...WHILE THE UKMET/CANADIAN HAVE TRENDED WEAKER AND SLOWER.
GIVEN THE WEAK STATE OF THE REMNANTS...PREFER THE WEAKER GFS
SOLUTION AT THIS TIME.

...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...

...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

JAMES

$$





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