Prognostic Meteorological Discussion
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FXUS10 KWNH 011854
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
254 PM EDT MON SEP 01 2014

VALID SEP 01/1200 UTC THRU SEP 05/0000 UTC

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

12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE
ECMWF


...TROUGH SLIDING FROM THE MIDWEST TO THE NORTHEAST THROUGH WED...

PREFERENCE: NON-GEM CONSENSUS
CONFIDENCE: AVERAGE

THIS TROUGH CONSISTS OF A LEAD SHORTWAVE AND A SMALLER SHORTWAVE
THAT QUICKLY FOLLOWS OVER THE NEXT COUPLE OF DAYS. THE COMBINATION
OF THE TWO WILL DRIVE A COLD FRONT THROUGH THE NORTHERN AND
NORTHEASTERN U.S...WHILE THE TAIL END STALLS IN THE MID MS VLY AND
CNTRL PLAINS. IN GENERAL THERE IS GOOD MODEL MASS FIELD AGREEMENT
WITH THE LARGER SCALE TROUGH AXIS. HOWEVER...THE 12Z GFS IS SEEN
AS BEING A TAD SLOWER THAN THE 12Z NAM AND THE REMAINING NON-NCEP
SOLNS INCLUDING THE 12Z UKMET/12Z GEM AND 12Z ECMWF. AT THE SFC
THOUGH......THE 12Z ECMWF AND 12Z UKMET HAVE TRENDED TWD THE 12Z
GFS AND 12Z NAM IDEA OF A RELATIVELY WEAKER/FLATTER WAVE THAT
IMPACTS THE ST LAWRENCE RIVER VALLEY AND SRN QUEBEC. THE 12Z GEM
IS NOW VIEWED AS A STRONG OUTLIER...AND EVEN THOUGH THE 00Z ECENS
MEAN SUPPORTS A STRONGER SFC WAVE...THE TRENDS IN THE 12Z GUIDANCE
COLLECTIVELY SUPPORT THE IDEA OF LEANING TWD A MORE
PROGRESSIVE/WEAKER SOLN. THEREFORE...WILL FAVOR A NON-GEM
CONSENSUS ATTM.


...PACIFIC TROUGH AFFECTING THE WEST AND SPILLING INTO THE
NORTHERN PLAINS LATE WED...
...LINGERING TROUGH/WEAKNESS LEFT OVER THE NORTHWEST...

PREFERENCE: BLEND OF 12Z GFS AND 12Z ECMWF
CONFIDENCE: AVERAGE

THE MODELS INDICATE A PROGRESSIVE BUT RATHER VIGOROUS TROUGH
DIGGING INTO THE NORTHWEST ON TUES AND THEN MOVING EAST OUT INTO
THE NRN PLAINS BY WED. MEANWHILE...ALL OF THE MODELS BY WED AND
THURS SHOW A TAIL OF ENERGY OR WEAKNESS LEFT BEHIND THE MAIN
SHORTWAVE TROUGH THAT WILL BE SITUATED OVER THE NORTHWEST AND DOWN
INTO NRN CA WHERE IT WILL BE ATTEMPTING TO INTERACT WITH ENERGY
OFFSHORE OF CA. THE 12Z UKMET AND 12Z GEM ARE FASTER WITH THE
HEIGHT FALLS THAT EJECT OUT ACROSS THE NRN PLAINS VS THE
RELATIVELY SLOWER 12Z GFS/12Z NAM AND 12Z ECMWF. THE SAME APPLIES
TO THE SFC LOW EVOLUTION THROUGH THE PERIOD...ALTHOUGH THE 12Z NAM
IS SEEN MOST TIME FRAMES AS BEING A TAD NORTH OF THE GLOBAL MODEL
CONSENSUS. THE LATEST GEFS MEAN AND ECENS MEAN FAVOR A SOMEWHAT
SLOWER SOLN AND SUPPORT THE DETERMINISTIC GFS AND ECMWF CAMP. OVER
THE NORTHWEST ON WED AND THURS...THERE IS NOT AS MUCH SPREAD WITH
THE GUIDANCE. BASED ON THE CURRENT DEGREE OF SPREAD AND
CLUSTERING...FEEL LIKE A BLEND OF THE 12Z GFS AND 12Z ECMWF WILL
SUFFICE FOR THE TIME BEING.


...BROAD AREA OF LOW PRESSURE ENTERING THE BAY OF CAMPECHE...

PREFERENCE: LATEST NHC TROPICAL WEATHER OUTLOOK

A BROAD AREA OF LOW PRESSURE IS ADVANCING INTO THE BAY OF CAMPECHE
FROM THE YUCATAN PENINSULA TODAY. THE NATIONAL HURRICANE CENTER
FORECASTS A 80 PERCENT CHANCE OF TROPICAL CYCLONE FORMATION WITHIN
THE NEXT 48 HOURS. THE MODEL SPREAD REMAINS RATHER MINIMAL
REGARDING THE TRACK...WITH THE GUIDANCE SUGGESTING THAT THE LOW
CENTER MOVES INTO NERN MEXICO BY WED. HOWEVER...IT SHOULD BE NOTED
THAT THE 12Z NAM AND 12Z UKMET SHOW CONSIDERABLY MORE VERTICAL
DEVELOPMENT AND ORGANIZATION COMPARED TO THE RELATIVELY WEAKER 12Z
GFS AND 12Z ECMWF. THE 12Z GEM TENDS TO SPLIT THE DIFF. PLS
CONSULT THE LATEST NHC TROPICAL WEATHER OUTLOOK FOR MORE
INFORMATION ON THIS SYS.


...EASTERLY WAVE APPROACHING FLORIDA...

PREFERENCE: NON-NAM CONSENSUS
CONFIDENCE: AVERAGE

AN EASTERLY WAVE APPROACHING THE BAHAMAS WILL BE ADVANCING ACROSS
SRN FL AND THE FL KEYS BY WED. THE 12Z NAM APPEARS TO BE TOO
STRONG WITH THE WAVE AXIS. THE 12Z GFS ALONG WITH THE 12Z GEM/12Z
UKMET AND 12Z ECMWF ARE A LITTLE WEAKER BUT ARE WELL CLUSTERED AT
THIS TIME WITH A TRACK GENERALLY OFF TO THE WEST. WILL PREFER A
NON-NAM CONSENSUS AS A RESULT.

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

ORRISON

$$




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