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Hurricane OPHELIA (Text)


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HURRICANE OPHELIA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU SEP 08 2005
 
THE LAST REPORT FROM AN AIR FORCE RESERVE HURRICANE HUNTER INDICATED
THAT THE CENTRAL PRESSURE OF OPHELIA HAD RISEN TO 990 MB...WITH
MAXIMUM FLIGHT LEVEL WINDS OF 74 KT.  A DROPSONDE IN THE SOUTHWEST
EYEWALL INDICATED 65-70 KT WINDS AT THE SURFACE...AND A SHIP JUST
EAST OF THE CENTER REPORTED 60 KT WINDS.  BASED ON THIS...THE
INITIAL INTENSITY REMAINS 65 KT.  DATA FROM THE MELBOURNE WSR-88D
SHOWS THAT SINCE 21Z THE CENTER OF OPHELIA HAS LOST SOME
ORGANIZATION...BECOMING BROADER AND WITH THE DOPPLER VELOCITIES
DECREASING.  A NOAA AIRCRAFT IS IN THE CENTER AS OF THIS WRITING AND
HAS JUST REPORTED A PRESSURE OF 991 MB.

WHILE THE INITIAL MOTION IS STILL NEARLY STATIONARY...THE CENTER IS
JUST A LITTLE NORTHEAST OF THE PREVIOUS POSITIONS.  IT IS TOO EARLY
TO TELL IF THIS IS THE START OF THE EXPECTED NORTHEASTWARD DRIFT. 
OPHELIA IS BETWEEN TWO MID-LEVEL RIDGES...WITH THE WESTERN RIDGE
WEAKENING AS A TROUGH MOVES TROUGH THE EASTERN UNITED STATES. 
TRACK GUIDANCE GENERALLY AGREES THAT OPHELIA WILL MOVE
NORTHEASTWARD FOR 2-3 DAYS UNTIL THE TROUGH GOES BY AND THE RIDGE
RE-BUILDS OVER THE EASTERN U.S..  HOWEVER...THERE ARE SIGNIFICANT
DIFFERENCES IN SPEED.  AFTER 72 HR...THE BUILDING RIDGE COULD CAUSE
A LOOPING MOTION OFF THE SOUTHEAST U.S. COAST THROUGH 120 HR...OR
EVEN MOVE THE STORM BACK TO THE COAST BEFORE 120 HR AS FORECAST BY
THE GFDL AND GFDN.  THE TRACK FORECAST WILL CALL FOR A SLOW
NORTHEASTWARD MOTION FOR 48-72 HR...FOLLOWED BY AN EQUALLY SLOW
LOOP BACK TO THE WEST...AND NOT FOLLOW THE FASTER EXTREMES OF THE
GUIDANCE EITHER EAST OR WEST.  THE NEW TRACK IS AN UPDATE OF THE
PREVIOUS TRACK.
 
THE INTENSITY FORECAST IS PROBLEMATIC.  ON THE SIDE FAVORING
STRENGTHENING...OPHELIA HAS A GOOD LOW-LEVEL STRUCTURE...IS OVER
THE WARM GULF STREAM...AND IS GENERATING CONVECTIVE TOPS NEAR -80C. 
ON THE SIDE INHIBITING STRENGTHENING...WATER VAPOR IMAGERY
INDICATES DRY AIR SURROUNDING OPHELIA...AND DATA FROM THE NOAA G4
JET SHOWS 20-30 KT OF SOUTHERLY FLOW AT 250 MB BLOWING RIGHT
THROUGH THE HURRICANE.  ADDITIONALLY...THE SLOW MOTION INTRODUCES
THE POSSIBILITY THAT OPHELIA WILL UPWELL COLDER WATER UNDERNEATH IT
IF IT MOVES OUT OF THE GULF STREAM.  SHIPS AND THE GFDL BOTH CALL
FOR STRENGTHENING...ALTHOUGH SHIPS MAY BE UNDERESTIMATING THE
WESTERLY SHEAR NEAR THE STORM AFTER 48 HR.  INDEED...MOST
LARGE-SCALE MODELS SHOW AN UPPER-LEVEL TROUGH NEAR THE SOUTHEAST
U.S. COAST AT 72 HR...WHICH IS AN ANOTHER COMPLICATION.  GIVEN THE
UNCERTAINTY...THE INTENSITY FORECAST WILL BE UNCHANGED FROM THE
PREVIOUS PACKAGE...AND A SOMEWHAT LOWER INTENSITY THAN FORECAST BY
SHIPS AND THE GFDL.
 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/0300Z 28.7N  79.3W    65 KT
 12HR VT     09/1200Z 29.0N  79.1W    70 KT
 24HR VT     10/0000Z 29.6N  78.5W    70 KT
 36HR VT     10/1200Z 30.2N  77.8W    75 KT
 48HR VT     11/0000Z 30.6N  77.0W    75 KT
 72HR VT     12/0000Z 31.0N  76.0W    80 KT
 96HR VT     13/0000Z 30.0N  76.0W    80 KT
120HR VT     14/0000Z 30.0N  77.0W    80 KT
 
 
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Page last modified: Friday, 09-Sep-2005 03:10:08 UTC