Prognostic Meteorological Discussion
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FXUS10 KWNH 151857
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
257 PM EDT MON SEP 15 2014

VALID SEP 15/1200 UTC THRU SEP 19/0000 UTC

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

12Z MODEL EVALUATION WITH FINAL PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z
NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS.


COLD FRONT IN THE VICINITY OF THE SOUTHEAST U.S.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: NON 12Z NAM COMPROMISE
CONFIDENCE: AVERAGE

THERE IS GOOD MODEL AGREEMENT ON THE DEPTH OF THE ASSOCIATED UPPER
TROUGHING OVER THE ERN HALF OF THE NATION AND AT THE SURFACE WITH
THE PROGRESSION OF THE FRONT THROUGH THE SOUTHEAST. THE BIGGEST
DIFFERENCES HAD BEEN WITH A WEAK WAVE OF LOW PRESSURE NEAR
GEORGIA/SOUTH CAROLINA FOR TUESDAY/WEDNESDAY...BUT THE LATEST
MODELS OUTSIDE OF THE 12Z NAM SHOW REASONABLE AGREEMENT WITH EACH
OTHER AND THE ENSEMBLE MEANS. THE 12Z NAM STANDS OUT AS A
FASTER/STRONGER OUTLIER WITH THIS SURFACE LOW AS IT TRACKS OFF
INTO THE ATLANTIC. A NON-12Z NAM COMPROMISE IS PREFERRED GIVEN THE
LATEST MODEL POSITIONS.


WEAK SURFACE LOW/TROUGH IMPACTING THE WESTERN GULF COAST TONIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: GENERAL MODEL COMPROMISE
CONFIDENCE: ABOVE AVERAGE

A GENERAL MODEL COMPROMISE IS PREFERRED DUE TO GOOD MODEL
AGREEMENT AND THE SHORT TERM FORECAST NATURE OF THIS SYSTEM.


LARGE UPPER TROUGH TO APPROACH NEARING NRN CALIFORNIA THU NIGHT
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z ECMWF / 12Z UKMET BLEND
CONFIDENCE: AVERAGE

ENSEMBLE SPAGHETTI HEIGHTS HAVE SHOWN A SLOWING TREND OVER THE
PAST 3 12/00Z CYCLES WITH THIS TROUGH...WITH THE 09Z SREF AND 12Z
GEFS MEANS FASTER BY THU EVENING OVER CALIFORNIA THAN THE 00Z EC
MEAN WITH THE UPPER TROUGH AXIS. THIS COULD BE DUE TO UPSTREAM
AMPLIFICATION OF THE PATTERN OVER THE E-CNTRL PACIFIC. LATE THU IS
THE ONLY SIGNIFICANT MODEL TIMING DIFFERENCE...AND GOOD RUN TO RUN
CONTINUITY EXISTS IN BOTH THE SLOWER ECMWF AND FASTER GFS OVER
THEIR PAST FEW 12/00Z CYCLES. THE LATEST 12Z UKMET/ECMWF HAVE
TRENDED SLOWER/FASTER RESPECTIVELY...WHICH SPLITS THE DIFFERENCE
BETWEEN THE FASTER AND SLOWER MODEL CAMPS. THE PRELIMINARY
PREFERENCE TO SPLIT THE DIFFERENCE BUT LEAN TOWARD THE SLOWER SIDE
OF THE SPREAD IS NOW BETTER REPRESENTED BY A BLEND OF THE 12Z
ECMWF/UKMET.


COLD FRONT INTO THE GREAT LAKES AND NORTHEAST ON WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 12Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE MIDDLE OF THE LATEST MODEL SPREAD IS BEST REPRESENTED BY A
GFS/ECMWF BLEND. THE 12Z UKMET/CMC ARE STRONGER WITH A WEAK LOW
ALONG THE FRONT IN SRN QUEBEC BUT HAVE TRENDED WEAKER FROM THEIR
00Z CYCLES...WHILE THE NAM IS MUCH FASTER WITH THIS FEATURE AND
THE RESULTING COLD FRONT THROUGH THE OHIO VALLEY AND NORTHEAST.


HURRICANE ODILE AND RELATED MOISTURE INTO THE SOUTHWEST
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 15Z NHC TRACK CLOSEST TO 12Z UKMET THROUGH 00Z/19

THE 15Z NHC ADVISORY FOR HURRICANE ODILE MOST CLOSELY MATCHED THE
12Z UKMET THROUGH 00Z/18...WITH THE GFS FASTER OVER THE NEXT 24
HOURS ENDING 00Z/19. THE 12Z ECMWF IS RELATIVELY UNCHANGED FROM
ITS 00Z RUN WITH THE LOW CENTER AND SLIGHTLY QUICKER WITH THE
MID-LEVEL ENERGY FROM ODILE.

THE 12Z NAM IS THE LEAST SUPPORTED BY NHC OR THE LATEST GUIDANCE
SUITE WITH ITS DEPICTION OF THE MID-LEVEL VORT CENTER TRACKING
NORTH ALONG THE BAJA PENINSULA WITH WEAKENING...AND A WWD TRACK
RELATIVE THE REMAINING MODELS. IN ADDITION...THE NAM FORMS A
SECONDARY VORT APPROACHING ARIZONA BY WED EVENING BUT IS NOT
SUPPORTED AT THIS TIME.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...


OTTO

$$





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