Prognostic Meteorological Discussion
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FXUS10 KWNH 151712
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
112 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 NAM/GFS EVALUATION WITH PRELIMINARY 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: BLEND OF THE 12Z GFS / 00Z ECMWF
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 EXIST WITH A WEAK WAVE OF LOW PRESSURE NEAR
GEORGIA/SOUTH CAROLINA FOR TUESDAY/WEDNESDAY. THE ENSEMBLE MEANS
SUPPORT A BLEND OF THE GFS/ECWMF WITH REASONABLE RUN TO RUN
CONSISTENCY IN PLACE.


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: 70% 00Z ECMWF / 30% 12Z GFS 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 06Z
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. HOWEVER...GIVEN THE TRENDS...AND
DESPITE THE RELATIVELY SMALL 150 MILE DIFFERENCE SEEN WITH THE
UPPER TROUGH AXIS BY 00Z/19...A BLEND OF THE TWO CAMPS IS
PREFERRED BUT WITH MORE WEIGHT TOWARD THE SLOWER SIDE OF THE
GUIDANCE IS PREFERRED...BEST REPRESENTED BY A 70 PERCENT BLEND OF
THE 00Z ECMWF AND 30 PERCENT WITH THE 12Z GFS.


COLD FRONT INTO THE GREAT LAKES AND NORTHEAST ON WED
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: 12Z GFS / 00Z ECMWF BLEND
CONFIDENCE: AVERAGE

THE MIDDLE OF THE LATEST MODEL SPREAD IS BEST REPRESENTED BY A
GFS/ECMWF BLEND. THE 00Z UKMET/CMC ARE STRONGER WITH A WEAK LOW
ALONG THE FRONT IN SRN QUEBEC...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 00Z UKMET THROUGH 00Z/19

THE 15Z NHC ADVISORY FOR HURRICANE ODILE MOST CLOSELY MATCHED THE
00Z UKMET AND 12Z GFS THROUGH 00Z/18...BUT THE GFS BECOMES FASTER
OVER THE NEXT 24 HOURS ENDING 00Z/19. THE 00Z ECMWF IS A BIT
SLOWER THAN THE NHC ADVISORY AS WELL AS THE 00Z CMC. 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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