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Tropical Storm OPHELIA (Text)

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TROPICAL STORM OPHELIA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
500 PM AST WED SEP 21 2011

OPHELIA HAS CHANGED LITTLE IN ORGANIZATION OVER THE PAST SEVERAL
HOURS...WITH A PORTION OF THE INNER CORE LOW-LEVEL CIRCULATION
STILL EXPOSED OVER THE SOUTHWEST SEMICIRCLE.  RECENT IMAGES SHOW
THAT THE CENTER IS LOCATED JUST UNDER THE SOUTHWEST EDGE OF THE
CONVECTIVE CANOPY.  MODERATE SOUTH-SOUTHWESTERLY SHEAR...ASSOCIATED
WITH AN UPPER-LEVEL TROUGH TO THE NORTHWEST OF THE STORM...IS
FORECAST TO CONTINUE TO AFFECT OPHELIA THROUGH THE FORECAST PERIOD. 
THEREFORE NO STRENGTHENING IS FORECAST...WITH SOME WEAKENING LIKELY
IN A FEW DAYS.  SINCE THE CURRENT LGEM GUIDANCE IS A LITTLE HIGHER
THAN THE PREVIOUS ONE...THE NHC WIND FORECAST NOW SHOWS LESS
WEAKENING IN 3-5 DAYS.  TWO MODEL EXTREMES HIGHLIGHT THE
UNCERTAINTIES IN PREDICTING INTENSITY CHANGE.  THE EXPERIMENTAL
COAMPS-TC MODEL...WHICH HAS BEEN A GOOD PERFORMER SO FAR THIS
YEAR...SHOWS DISSIPATION BY 72 HOURS WHILE THE GFDL MODEL PREDICTS
OPHELIA TO BECOME A MAJOR HURRICANE BY THE END OF THE FORECAST
PERIOD.

INITIAL MOTION REMAINS AROUND 280/14 AS THE STORM REMAINS SOUTH OF A
SUBTROPICAL HIGH PRESSURE SYSTEM.  OPHELIA IS LIKELY TO MOVE ON A
WESTWARD TO WEST-NORTHWESTWARD TRACK OVER THE NEXT SEVERAL
DAYS...ALONG THE SOUTHERN PERIPHERY OF THE HIGH.  LATE IN THE
FORECAST PERIOD...AS THE CYCLONE NEARS THE SOUTHWESTERN PERIPHERY
OF THE RIDGE...THE DYNAMICAL GUIDANCE IS LEANING MORE TO THE RIGHT
OF PREVIOUS RUNS.  THE LATEST OFFICIAL FORECAST IS A LITTLE TO THE
NORTH...OR RIGHT...OF THE PREVIOUS ONE BUT NOT AS FAR TO THE RIGHT
AS MOST OF THE TRACK MODELS BY DAY 5.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/2100Z 13.6N  44.7W   50 KT  60 MPH
 12H  22/0600Z 13.8N  46.8W   50 KT  60 MPH
 24H  22/1800Z 14.1N  49.4W   50 KT  60 MPH
 36H  23/0600Z 14.6N  51.8W   50 KT  60 MPH
 48H  23/1800Z 15.5N  54.0W   50 KT  60 MPH
 72H  24/1800Z 17.5N  58.5W   45 KT  50 MPH
 96H  25/1800Z 20.0N  62.5W   45 KT  50 MPH
120H  26/1800Z 22.5N  65.5W   45 KT  50 MPH
 
$$
FORECASTER PASCH
 
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