Prognostic Meteorological Discussion
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000
FXUS10 KWNH 031641
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1240 PM EDT THU SEP 03 2015

VALID SEP 03/1200 UTC THRU SEP 07/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS

...NEGATIVELY-TILTED TROUGH CROSSING THE NORTHWEST...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z NAM AND 00Z UKMET TEND TO BE STRONGER OUTLIERS WITH THE
EVOLVING DEEP TROUGH THAT GOES NEG-TILT ACROSS THE NORTHWEST AND
OUT INTO THE HIGH PLAINS OVER THE NEXT TWO TO THREE DAYS. THE
STRONGER MODEL CLUSTERING TENDS TO FAVOR THE 12Z GFS AND 00Z
ECMWF...AND BOTH OF THESE MODELS HAVE DECENT SUPPORT FROM THE 00Z
CMC AND ALSO THE LATEST GEFS MEAN AND ECENS MEAN. THUS...A BLEND
OF THE GFS AND ECMWF WILL BE PREFERRED.


...MID LEVEL TROUGH/CLOSED LOW CENTER OVER MI...

PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

A RATHER COMPACT MID LEVEL TROUGH AND ASSOCIATED CLOSED LOW OVER
LOWER MI IS EXPECTED TO LINGER HERE OVER THE NEXT COUPLE OF DAYS
BEFORE THEN WEAKENING THIS WEEKEND AND GRADUALLY SHEARING THROUGH
SOUTHEAST ONTARIO. THE 12Z NAM AND 00Z CMC TEND TO HANG ONTO
STRONGER HEIGHT FALLS WITH THIS SYSTEM BEFORE GRADUALLY WEAKENING
THE ENERGY. OVERALL...THE MODEL SPREAD IS NOT PARTICULARLY
SIGNIFICANT...BUT WILL AGAIN SUGGEST A BLEND OF THE 12Z GFS AND
00Z ECMWF GIVEN BETTER OVERALL CLUSTERING AND ENSEMBLE SUPPORT.


...RETROGRADING UPPER LOW MOVING INTO THE SOUTHEAST SAT/SUN...

PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF AND 00Z UKMET
CONFIDENCE: AVERAGE

THE MODELS INDICATE DEVELOPMENT OF A REX BLOCK ALONG AND JUST
OFFSHORE THE EAST COAST BY SAT. THE UPPER LOW DEVELOPING OFF THE
SOUTHEAST COAST IS FORECAST TO SLOWLY RETROGRADE INTO THE INTERIOR
SOUTHEAST BY LATE SUN. SURFACE LOW PRESSURE ASSOCIATED WITH THIS
APPEARS IN PART TO BE RELATED TO THE REMNANTS OF FORMER T.S.
ERIKA. THE 00Z CMC OVERALL IS THE DEEPEST SOLUTION WITH THE
EVOLUTION OF ALL OF THIS ENERGY. THE 12Z GFS/00Z ECMWF AND 00Z
UKMET ARE ALL A LITTLE WEAKER ALOFT AND WITH THE SURFACE PRESSURE
FIELDS. THE 12Z NAM APPEARS TO BE TOO FAR EAST WITH ITS SURFACE
AND MID LEVEL LOW CENTERS.


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

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

ORRISON
$$





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