Prognostic Meteorological Discussion
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000
FXUS10 KWNH 210700
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
259 AM EDT SUN SEP 21 2014

VALID SEP 21/0000 UTC THRU SEP 24/1200 UTC

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

==============================================
00Z MODEL EVALUATION AND PREFERENCES
==============================================
NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO
SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT.
==============================================

...EASTERN U.S...INCLUDING A COASTAL LOW...

PREFERENCE DAY 2:  BLEND OF 21/00Z NAM/GFS
PREFERENCE DAY 3:  21/00Z NAM/GFS AND/OR 20/12Z GEFS MEAN
CONFIDENCE: AVERAGE

MODELS ARE NOW SIMILAR IN HANDLING THE TRACK AND TIMING OF COASTAL
LOW PRESSURE AS IT PARALLELS THE ATLANTIC COAST BEFORE BEING
ABSORBED AHEAD OF A SYNOPTIC LOW/FRONT NEAR NEW ENGLAND. THE
21/00Z NAM BACKED AWAY FROM ITS DEEPER SOLN IN HOW IT HANDLES THE
TROF OVER THE EASTERN STATES GETTING IT IN BETTER OVERALL
AGREEMENT WITH THE GFS AND THE PREVIOUS GEFS MEAN.  THE GFS
CONTINUITY WAS PRETTY GOOD IN HANDLING THIS FEATURE WHEN COMPARED
WITH THE 20/12Z GFS. WHILE THE ECMWF HAD A DIFFERENT TAKE ON THE
EAST COAST SYSTEM...ESPECIALLY OVER THE SOUTHEAST ON DAY 3...IT
KEPT PRETTY GOOD CONTINUITY WITH ITS PREVIOUS RUN IN THE MID
LEVELS.  00Z MODEL RUNS FROM NCEP AND THE UKMET ALONG WITH THE 12Z
GEFS WOULD POINT AWAY FROM THE EC IDEA AT THIS POINT...ALTHOUGH
THE 00Z CANADIAN LIKES THE IDEA OF A WEAKNESS BETWEEN TWO MID
LEVEL HIGHS BUT NOT TO THE ECMWF SOLN.  THINK A NON EC SOLN AT
THIS POINT IS STILL BEST.

...SHEAR AXIS TRAPPED IN THE UPPER RIDGE BUILDING OVER THE
SOUTHERN PLAINS...

PREFERENCE: A NON NAM BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: AVERAGE

OVERALL AGREEMENT IN THE MODEL MASS FIELDS WAS GOOD HERE EXCEPT
FOR THE NAM...WHICH BECOMES A BIT OF AN EASTWARD OUTLIER IN TERMS
OF WHERE IT PLACES MOISTURE ON DAY 3.

...SYSTEM TRACKING FROM CALIFORNIA TO THE NORTHERN PLAINS...

PREFERENCE: ANY OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

THE OPERATIONAL MODELS STILL SHOW STRONG AGREEMENT AT THE SURFACE
AND ALOFT.


...DEEP TROUGH LEANING INTO THE PACIFIC NORTHWEST...

PREFERENCE: ANY OF THE 00Z NCEP/ECMWF/UKMET RUNS...LESS WEIGHT ON
THE CANADIAN
CONFIDENCE: ABOVE AVERAGE

A LEAD SHORTWAVE WILL BRING HEIGHT FALLS AND THE ONSET OF LIGHT
PRECIPITATION WEST OF THE WA/OR CASCADES ON MONDAY. THE WAVE WILL
PUSH A WEAK BOUNDARY INTO THE NORTHERN ROCKIES MON/TUE. A DEEPER
LONGWAVE TROUGH WILL APPROACH THE COAST BY LATE TUESDAY AND INTO
WEDNESDAY. MODEL AGREEMENT IN THE 00Z PRODUCTION CYCLE IS STILL
STRONG...ASIDE FROM THE CANADIAN WHICH HAS CONTINUED TO SHOW MORE
RUN TO RUN VARIABILITY WITH RESPECT TO SHORTWAVE TIMING AND
STRENGTH.

...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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