Prognostic Meteorological Discussion
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000
FXUS10 KWNH 220504
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
103 AM EDT MON SEP 22 2014

VALID SEP 22/0000 UTC THRU SEP 25/1200 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 INTO TUESDAY...

PREFERENCE: ANY OF THE OPERATIONAL MODELS
CONFIDENCE: ABOVE AVERAGE

A WELL DEFINED CYCLONE WILL PUSH EAST FROM NEW ENGLAND...ABSORBING
A COASTAL LOW LIFTING UP FROM THE CAROLINAS. MODEL SPREAD IS
MINIMAL. THE ECMWF IMPROVED UPON ITS SURFACE SOLUTION WITH RESPECT
TO THE COASTAL LOW.


...EASTERN U.S LATE TUE THRU WED INTO EARLY THU...

PREFERENCE: 12Z ECMWF ENSEMBLE MEAN...WITH GROWING SUPPORT
CONFIDENCE: AVERAGE

WHILE THE 00Z MODELS DISPLAYED SOME DIFFERENCES BY LATE
TUESDAY...THE SPREAD GETS LARGER THROUGHOUT THE REMAINDER OF DAY 2
INTO DAY 3.  EARLIER RECOMMENDATION FOR USING THE ECMWF ENSEMBLE
MEAN STILL LOOKS GOOD CONSIDERING ITS CONSISTENCY AND THE
AGREEMENT IT HAS WITH THE ECMWF OPERATIONAL RUN.  THE GEFS SUPPORT
OF THE 21/12Z OR 22/00Z GFS WAS NOT NEARLY AS GOOD.  SO WILL
CONTINUE TO RECOMMEND THIS IDEA.

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

PREFERENCE: BLEND OF THE OPERATIONAL MODELS
CONFIDENCE: AVERAGE

THE 00Z MODELS STILL STRUGGLE TO MAINTAIN DEFINITION WITH A 850 TO
700 MB SHEAR AXIS TRAPPED BENEATH AN UPPER LEVEL RIDGE.  THE MODEL
SOLUTIONS ARE SIMILAR BUT CONFIDENCE REGARDING DETAILS OF
CONVECTION IN A QUASI TROPICAL AIRMASS DECREASES WITH TIME OWING
TO CONTINUED SMALL SCALE FEEDBACK BEING OBSERVED AND NOT OFTEN
APPEARING IN THE MODELS.


...SYSTEM TRACKING FROM THE GREAT BASIN INTO THE PLAINS...

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

THERE HAS BEEN A TREND FOR THE MODELS TO SLOW THIS SYSTEM AND
DEPICT A SOMEWHAT MORE PRONOUNCED CIRCULATION BY THE TIME IT PULLS
INTO THE CENTRAL PLAINS...ALTHOUGH THE GFS AND ECMWF BEGAN TO TAKE
INDIVIDUAL SHORTWAVES EASTWARD MORE QUICKLY.  BLENDING THE 00Z
GFS/UKMET AND THE 21/12Z SHOULD KEEP THE ESSENCE OF THE LARGE
SCALE FEATURE WHILE MITIGATING SOME OF THE PROBLEMS WITH THE MINOR
SHORTWAVES.

...DEEP TROUGH WITH INCREASING IMPACT TO THE PACIFIC NORTHWEST...

PREFERENCE: BLEND OF THE 00Z OPERATIONAL MODELS...LESS WEIGHT ON
THE NAM
CONFIDENCE: ABOVE AVERAGE

THIS TROUGH WILL BEING TO PRODUCE MORE MEANINGFUL IMPACTS AND
WIDESPREAD RAIN BY WEDNESDAY. MODEL SPREAD IS MINIMAL.

...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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