Prognostic Meteorological Discussion
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FXUS10 KWNH 011652
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1251 PM EDT TUE SEP 01 2015

VALID SEP 01/1200 UTC THRU SEP 05/0000 UTC

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

12Z NAM/GFS EVALUATION...

UPPER TROUGH FORMING ACROSS THE PACIFIC NORTHWEST...

PREFERENCE: 12Z GFS OR 00Z ECMWF
CONFIDENCE: ABOVE AVERAGE

THE GFS AND ECMWF ALIGN WELL WITH THE MODEL CONSENSUS INCLUDING
THE ENSEMBLE MEANS WITH NEAR TO BELOW NORMAL SPREAD BY DAY 3.
GIVEN REASONABLY GOOD RUN TO RUN CONTINUITY...THE NAM REMAINED A
SLOW OUTLIER COMPARED TO THE CONSENSUS.

UPPER LOW OVER THE LOWER MS VALLEY...

PREFERENCE: HALFWAY BETWEEN THE GFS AND ECMWF
CONFIDENCE: BELOW AVERAGE

THE SPREAD REMAINS VERY HIGH CONCERNING THE DETAILS OF THE
STRUCTURE OF THE EVOLVING LOW.  HOWEVER...THERE ARE SOME
INDICATIONS TO LEAN SOMEWHERE BETWEEN THE GFS AND ECMWF....WITH
THE NAM TRENDING EASTWARD BUT STILL NEAR WESTERN EDGES OF THE
GUIDANCE BY DAY 3...THE GFS TRENDING EASTWARD...AND THE ECMWF
TRENDING WESTWARD.  THUS...A SOLUTION ABOUT MIDWAY BETWEEN THE GFS
AND ECMWF IS PREFERRED.

REMNANTS OF ERIKA...

PREFERENCE: GFS OR ECMWF
CONFIDENCE: AVERAGE

THE GFS AND ECMWF STILL APPEAR TO CAPTURE THE SUBSIDENCE RING
DEVELOPING OVER SOUTHERN FLORIDA TODAY AND TONIGHT BETTER THAN THE
NAM.  THUS...RECOMMEND EITHER THE GFS OR ECMWF.

SHORTWAVE PATTERN ACROSS THE GREAT LAKES/OH VALLEY THU-FRI...

PREFERENCE: ENSEMBLE MEANS
CONFIDENCE: BELOW AVERAGE

THE 12Z GFS CONTINUED TO HAVE PROBLEMS WITH RESPECT TO HOW IT
HANDLES THE SHORTWAVE ENERGY APPROACHING THE LONG WAVE RIDGE
POSITION...STILL LOOKING TO BE TOO FAST.  THE 01/00Z ECMWF WA NEAR
THE STRONG EDGE OF THE GUIDANCE WITH A SHORTWAVE TROUGH EXITING
THE ROCKIES AND REACHING THE CENTRAL PLAINS.  THE NAM IN BETWEEN
THESE MORE EXTREME SOLUTIONS BUT HAS ITS OWN ISSUES WITH PLACEMENT
AND STRENGTH OF A NORTHERN LEE LOW.  TO ADDRESS THESE
CONCERNS...WE STILL RECOMMEND THE ENSEMBLE MEANS UNTIL BETTER
DETERMINISTIC AGREEMENT DEVELOPS.

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

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

BANN

$$





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