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Hurricane OPHELIA


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TROPICAL STORM OPHELIA DISCUSSION NUMBER  29
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT TUE SEP 13 2005
 
DATA FROM SATELLITES...DOPPLER RADARS...AND AN AIR FORCE
RECONNAISSANCE AIRCRAFT INDICATE OPHELIA HAS BECOME A LITTLE BETTER
ORGANIZED THIS MORNING AND IS JUST BELOW HURRICANE STRENGTH. THE
HIGHEST RECON 700 MB FLIGHT-LEVEL HAS BEEN 66 KT IN THE NORTHEAST
QUADRANT. DOPPLER VELOCITY DATA FROM WILMINGTON HAS BEEN RUNNING
67-70 KT BETWEEN 10000 TO 12000 FEET IN THE NORTHEAST QUADRANT...
JUST TO THE NORTHWEST OF THE RECON MAX WIND REPORT. THESE VALUES
WOULD SUPPORT 59-63 KT SURFACE WINDS...AND THE INITIAL INTENSITY IS
A BLEND OF THESE VALUES.
 
THE INITIAL MOTION ESTIMATE IS 330/03 OVER THE PAST 9-12 HOURS. A
SMALL INNER-CORE CIRCULATION WITH CONVECTION HAS BEEN ROTATING
CYCLONICALLY AROUND THE INSIDE OF THE LARGER RADIUS OF MAXIMUM
WINDS. THIS HAS RESULTED IN SPITS AND SPURTS OF FORWARD MOTION...
INCLUDING SMALL LOOPS. HOWEVER...THE LARGER CIRCULATION AND
PRESSURE FIELD APPEAR TO BE MOVING SLOWLY BUT STEADILY TOWARD THE
NORTH CAROLINA COAST. THE LATEST 12Z UPPER-AIR DATA INDICATES A
SMALL MID- TO UPPER-LEVEL HIGH PRESSURE CELL HAS MOVED FROM WEST
VIRGINIA TO NEW JERSEY DURING THE PAST 24 HOURS...DURING WHICH TIME
THE HEIGHTS HAVE DECREASED BY AT LEAST 30-40 METERS. AS THIS
FEATURE CONTINUES TO MOVE EAST-NORTHEASTWARD OFF THE NORTHEAST U.S.
COAST...THE STEERING FLOW SHOULD BECOME MORE SOUTHERLY AND ALLOW
OPHELIA TO GRADUALLY LIFT NORTHWARD DURING THE NEXT 24 HOURS. AFTER
THAT...THE NHC MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON THE
CYCLONE TURNING SLOWLY NORTHEASTWARD AND CROSSING THE NORTH
CAROLINA OUTER BANKS IN ABOUT 48 HOURS BEFORE ACCELERATING
EAST-NORTHEASTWARD AHEAD OF A STRONG SHORTWAVE TROUGH AND FRONTAL
SYSTEM. THE OFFICIAL FORECAST TRACK IS CLOSE TO THE PREVIOUS TRACK
THROUGH 48 HOURS...AND THEN FASTER AND A LITTLE TO THE RIGHT AFTER
THAT. THIS IS CONSISTENT WITH BUT TO THE RIGHT OF THE NHC MODEL
CONSENSUS DUE TO MORE WESTERLY MID-LEVEL FLOW ACTING TO DRIVE THE
CYCLONE MORE TO THE EAST AT HIGHER LATITUDES AT DAYS 4 AND 5.
 
THE INNER CORE OF OPHELIA IS MOVING OVER THE WARMER GULFSTREAM WHERE
SSTS ARE 82F-83F. THE WARMER WATER HAS LIKELY HELPED TO GENERATE
SOME MODERATE CONVECTION AROUND THE WIND CENTER. HOWEVER...THERE IS
STILL A LOT OF DRY AIR IN THE INNER REGION THAT HAS TO BE MIXED OUT
BEFORE ANY SIGNIFICANT STRENGTHENING CAN OCCUR. ONCE OPHELIA NEARS
THE COAST OF THE CAROLINAS WHERE SSTS DROP BY ABOUT 3F-5F...THERE
MAY BE SOME EROSION OF THE INNER CORE CONVECTION. HOWEVER...GIVEN
THE LARGE SIZE OF THE RADIUS IF MAXIMUM WINDS...ONLY SLOW INTENSITY
CHANGES UP OR DOWN SHOULD OCCUR BEFORE...DURING...AND AFTER
LANDFALL. UPPER-LEVEL OUTFLOW IS EXPECTED TO REMAIN QUITE FAVORABLE
FOR THE NEXT 36-48 HOURS...SO SOME MODEST STRENGTHENING IS POSSIBLE
AND OPHELIA COULD PEAK AT 70 KT BEFORE LANDFALL OCCUR. ONCE OPHELIA
CLEARS THE OUTER BANKS...INCREASING WESTERLY SHEAR SHOULD INDUCE
SLOW WEAKENING UNTIL THE CYCLONE TRANSITIONS INTO AN EXTRATROPICAL
LOW PRESSURE SYSTEM OVER THE COLD WATERS OF THE NORTH ATLANTIC.
 
FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      13/1500Z 32.3N  78.0W    60 KT
 12HR VT     14/0000Z 32.9N  78.1W    65 KT
 24HR VT     14/1200Z 33.9N  77.7W    65 KT
 36HR VT     15/0000Z 34.9N  76.9W    65 KT...INLAND
 48HR VT     15/1200Z 35.4N  75.7W    65 KT...INLAND/PAMLICO SOUND
 72HR VT     16/1200Z 36.7N  72.7W    60 KT
 96HR VT     17/1200Z 41.0N  65.5W    55 KT...BECOMING EXTRATROPICAL
120HR VT     18/1200Z 47.0N  53.5W    45 KT...EXTRATROPICAL
 
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