Prognostic Meteorological Discussion
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000
FXUS10 KWNH 200648
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
148 AM EST THU NOV 20 2014

VALID NOV 20/0000 UTC THRU NOV 23/1200 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.
==============================================

...NORTHWEST U.S. AND NORTHERN ROCKIES...

PREFERENCE: BLEND OF 20/00Z GFS/ECMWF
CONFIDENCE: AVERAGE

A PRONOUNCED SHORTWAVE TROUGH AND STRONG WESTERLY FLOW WILL BREAK
THROUGH THE RIDGE OVER THE PACIFIC NORTHWEST AND SPREAD DOWNSTREAM
INTO THE NORTHERN ROCKIES BY SATURDAY. MODELS ARE FAIRLY
SIMILAR...ALTHOUGH THE UKMET STANDS OUT AS BEING FAST. THE 00Z
GFS/ECMWF AND ESPECIALLY THE NAM WERE SLOWER.  THE GFS RUN TO RUN
CONTINUITY WAS GOOD WHILE THE 00Z NAM WAS SLOWER THAN THE 19/12Z
RUN.  THE NEW ECMWF DEPICTED THE WAVE HAVING LESSER AMPLITUDE ONCE
IT CLEARS THE NORTHERN ROCKIES.  THE DIFFERENCE WAS PRETTY SUBTLE
BUT GOT IT INTO BETTER AGREEMENT WITH ITS MEAN FROM THE DAYTIME
ENSEMBLES.

...SOUTHWEST U.S. AND SOUTHERN PLAINS...

PREFERENCE: BLEND OF 20/00Z GFS/ECMWF
CONFIDENCE: AVERAGE

A LOW AMPLITUDE LEAD WAVE WILL MOVE INTO THE SOUTHERN PLAINS BY
FRIDAY. THIS WILL BE FOLLOWED BY A MUCH STRONGER TROUGH DIVING
FROM CALIFORNIA INTO THE RIO GRANDE BASIN AND CROSSING TEXAS ON
DAY 3. WITH SHORT WAVELENGTH AND STRONG GRADIENTS...THIS IS A
DYNAMIC SYSTEM. SO THE VERY DEEP SOLUTION FROM THE UKMET AND ONLY
MARGINALLY WEAKER NAM RUNS CANNOT BE DISCOUNTED...BUT THE
ENSEMBLES SIMPLY DO NOT OFFER ANY SUPPORT.

...EASTERN / NORTHEASTERN U.S...

PREFERENCE: NON NAM BEYOND F72.
CONFIDENCE: ABOVE AVERAGE

THE NCEP MODELS HAD GOOD CONTINUITY WITH RESPECT TO THE A
SHORTWAVE SWINGING THROUGH THE LARGE SCALE FLOW PATTERN...

A SHORTWAVE TROUGH ROTATING THROUGH THE GREAT LAKES WILL BEGIN TO
SWING THE LARGER SCALE TROUGH EASTWARD...YIELDING MORE WARM
ADVECTION AND RIDGING INTO THE EASTERN U.S. BY FRIDAY AND
SATURDAY. ABOUT THE ONLY MODEL THAT GETS OUT OF STEP WITH THE
OTHER MODELS IS THE NAM AT ABOUT 23/00Z.  EVEN THEN...THE BIGGEST
DIFFERENCES ARE WELL OFF THE EAST COAST.  THE 00Z RUNS OF NON NCEP
MODELS WERE QUITE CONSISTENT WITH THEIR EARLIER RUNS.  GIVEN THE
VERY GOOD AGREEMENT IN THE MASS FIELDS OVER THIS REGION...THINK
ANY OF THE OPERATIONAL MODELS OR A CONSENSUS WORKS FINE.

...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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