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Tropical Storm OPHELIA


ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL STORM OPHELIA DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL162011
1100 AM AST FRI SEP 23 2011
 
THE SATELLITE APPEARANCE OF OPHELIA HAS CONTINUED TO DEGRADE AND THE
SYSTEM IS LOOKING LESS AND LESS LIKE A TROPICAL CYCLONE. DRY AIR
COUPLED WITH MODERATE TO STRONG SOUTH-SOUTHWESTERLY WIND SHEAR HAS
ERODED NEARLY ALL OF THE INNER CORE CONVECTION...AND WHAT DEEP
CONVECTION THAT DOES EXIST IS OCCURRING IN A RAGGED BAND MORE THAN
200 NMI EAST THROUGH SOUTH OF THE CENTER. THE INITIAL INTENSITY IS
DECREASED TO 35 KT BASED ON AN EARLIER WIND REPORT OF 31 KT FROM
NOAA BUOY 41041 LOCATED WELL EAST OF THE CENTER. NOAA BUOY 41040
JUST WEST OF THE CENTER HAS NOT SHOWN SIGNS OF THE SURFACE WINDS
BACKING AROUND TO A WESTERLY DIRECTION...WHICH SUGGESTS THAT
OPHELIA MIGHT JUST BE A SHARP OPEN WAVE. AN AIR FORCE RESERVE
RECONNAISSANCE AIRCRAFT WILL INVESTIGATE THE CYCLONE THIS AFTERNOON
BETWEEN 18-00Z TO SEE IF OPHELIA HAS A CLOSED SURFACE CIRCULATION.

THE INITIAL MOTION IS 280/14. SMOOTHING THROUGH ALL OF THE WIGGLES
AND WOBBLES...CAUSED BY BRIEF CONVECTIVE BURSTS NEAR THE CENTER...
OVER THE PAST 48 HOURS ALSO YIELDS A MOTION VECTOR OF 280 DEGREES.
AS CONTINUED STRONG VERTICAL SHEAR AND DRY AIR ENTRAINMENT TAKE
THEIR TOLL ON THE CONVECTIVE STRUCTURE AND ORGANIZATION OF
OPHELIA...THE VERTICAL DEPTH OF THE CYCLONE IS EXPECTED TO BECOME
INCREASINGLY SHALLOW. THE RESULT IS THAT THE CYCLONE SHOULD BE
STEERED MORE WESTWARD LIKE THE ECMWF AND UKMET ARE
FORECASTING...AND LESS POLEWARD LIKE THE MORE ROBUST GFDL AND HWRF
MODELS ARE INDICATING. ASSUMING OPHELIA STILL EXISTS BY DAYS 4 AND
5...A TURN TOWARD THE NORTHWEST AND NORTH IS EXPECTED AS THE
CYCLONE ROUNDS THE WESTERN PERIPHERY OF THE BERMUDA HIGH AND LIFTS
OUT POLEWARD AHEAD OF AN UPPER-LEVEL LOW EAST OF THE BAHAMAS. THE
OFFICIAL FORECAST TRACK IS TO THE LEFT OF THE PREVIOUS TRACK AND
THE CONSENSUS MODELS DUE TO THE UNREALISTIC NORTHWARD TRACK OF THE
HWRF MODEL...AND LIES ALONG THE SOUTHERN EDGE OF THE GUIDANCE
ENVELOPE NEAR A BLEND OF THE ECMWF...UKMET...AND SHALLOW BAM
MODELS.
 
THE 25-30 KT OF SOUTHWESTERLY TO WESTERLY VERTICAL SHEAR IS NOT
FORECAST TO ABATE FOR THE NEXT 4 DAYS OR SO...ALL THE WHILE THE
CYCLONE MOVES INTO AN EVEN DRIER AIR MASS. IT IS...THEREFORE...
POSSIBLE THAT OPHELIA COULD DEGENERATE INTO A REMNANT LOW OR EVEN
AN OPEN WAVE BY 48 HOURS LIKE THE STATISTICAL-DYNAMICAL MODELS
SHIPS AND LGEM ARE FORECASTING. HOWEVER...GIVEN THE RATHER LARGE
CIRCULATION OF OPHELIA AND THAT SSTS OF NEAR 29C LIE AHEAD OF THE
CYCLONE...THE OFFICIAL FORECAST CALLS FOR OPHELIA TO MAINTAIN SOME
CONVECTION AND AT LEAST TROPICAL DEPRESSION STATUS THROUGH DAY 4.
BY DAY 5...SOME SLIGHT INTENSIFICATION IS POSSIBLE ON AS THE SHEAR
DECREASES AND OPHELIA MOVES UNDER OR NEAR A SMALL UPPER-LEVEL
ANTICYCLONE.

FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 14.6N  52.6W   35 KT  40 MPH
 12H  24/0000Z 15.6N  54.6W   35 KT  40 MPH
 24H  24/1200Z 16.8N  56.9W   30 KT  35 MPH
 36H  25/0000Z 17.9N  58.8W   30 KT  35 MPH
 48H  25/1200Z 19.1N  60.9W   30 KT  35 MPH
 72H  26/1200Z 21.2N  64.3W   30 KT  35 MPH
 96H  27/1200Z 23.0N  66.5W   30 KT  35 MPH
120H  28/1200Z 25.5N  67.5W   35 KT  40 MPH
 
$$
FORECASTER STEWART
 
NNNN


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Page last modified: Tuesday, 17-Jul-2012 13:44:06 UTC