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Hurricane OPHELIA


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HURRICANE OPHELIA DISCUSSION NUMBER  20
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT SUN SEP 11 2005
 
AIR FORCE RECON MEASURED A PEAK 700 MB FLIGHT LEVEL WIND OF 85 KT
ABOUT 25 N MI WEST OF THE CENTER AS THEY DEPARTED FROM THEIR LAST
FIX AT AROUND 06Z.  THIS IS THE STRONGEST FLIGHT LEVEL WIND
REPORTED TO DATE IN OPHELIA AND SUPPORTS INCREASING THE INTENSITY
TO 75 KT.  THE MOST RECENT CENTRAL PRESSURE MEASURED BY DROPSONDE
WAS 978 MB...BASICALLY UNCHANGED DURING THE PAST SEVERAL HOURS.  THE
75 KT INTENSITY IS ALSO CONSISTENT WITH THE LATEST DVORAK
ESTIMATES... ALTHOUGH THE DATA T NUMBERS ARE ONLY 4.0 DUE TO THE
SLIGHT DEGRADATION OF THE SATELLITE APPEARANCE SINCE COMING OUT OF
THE GOES-12 ECLIPSE PERIOD... SO IT IS POSSIBLE THAT OPHELIA IS
AGAIN A LITTLE WEAKER THAN 75 KT.  WHILE OPHELIA MIGHT BE WITHIN AN
ENVIRONMENT MORE CONDUCIVE FOR STRENGTHENING ONCE THE UPPER LEVEL
RIDGE REACHES THE EAST COAST AND THE LONGITUDE OF THE HURRICANE IN
A COUPLE OF DAYS... THE SLOW MOTION OF OPHELIA COULD CAUSE OCEAN
UPWELLING AND PROVIDE A COUNTERACTING LIMITATION ON THE INTENSITY. 
GIVEN THIS REASONING AND THAT NONE OF THE INTENSITY GUIDANCE
FORECASTS SIGNIFICANT CHANGES... THE OFFICIAL FORECAST MAINTAINS 75
KT THROUGH 72 HOURS...FOLLOWED BY WEAKENING DUE TO INCREASING SHEAR
AND COOLER WATERS AHEAD OF THE NEXT MIDLATITUDE TROUGH.
 
OPHELIA REMAINS STATIONARY AND SANDWICHED BETWEEN STRONG AND DEEP
HIGH PRESSURE CENTERS OVER THE WESTERN HALF OF THE ATLANTIC AND
OVER THE EAST HALF OF THE UNITED STATES. LACKING A SUBSTANTIAL
CHANGE IN THIS PATTERN DURING THE NEXT COUPLE OF DAYS...VERY SLOW
MOTION IS EXPECTED. THE MIDLATITUDE PATTERN IS FORECAST BY THE
DYNAMICAL MODELS TO BECOME MORE PROGRESSIVE AND MOVE THE U.S. RIDGE
OFFSHORE IN ABOUT 3 DAYS...FOLLOWED BY THE NEXT TROUGH WHICH SHOULD
THEN FINALLY GET OPHELIA MOVING NORTHEASTWARD. PERHAPS DUE IN PART
TO THE SYNOPTIC SURVEILLANCE MISSION BY THE NOAA G-IV JET LAST
NIGHT... SOME OF THE DYNAMICAL MODELS HAVE COME INTO BETTER
AGREEMENT ON THE FORECAST TRACK. THE 00Z GFS HAS SHIFTED MORE THAN
100 MILES WESTWARD AND NOW FORECASTS LANDFALL OVER THE NORTH
CAROLINA OUTER BANKS IN THREE TO FOUR DAYS. THIS SHIFT BRINGS THE
GFS INTO REMARKABLY GOOD AGREEMENT WITH THE 00Z RUNS OF THE NOGAPS
AND UKMET. THE NEW OFFICIAL FORECAST IS ADJUSTED SOMEWHAT TO THE
EAST AT 72 HOURS...AND IS A LITTLE FASTER THERAFTER... TO CONFORM
WITH THIS GUIDANCE...BUT IS ESSENTIALLY UNCHANGED DURING THE PERIOD
OF SLOW MOTION THROUGH DAY TWO.
 
THE NEW FORECAST IMPLIES A LESSER POSSIBILITY OF OPHELIA DIRECTLY
IMPACTING THE EXTREME SOUTHERN END OF THE HURRICANE WATCH AREA...
SO A SMALL PORTION OF THE WATCH HAS BEEN DISCONTINUED...FROM EDISTO
BEACH SOUTHWARD.  HOWEVER... THROUGHOUT THE REMAINDER OF THE
HURRICANE WATCH AREA... SINCE OPHELIA IS NOT YET MOVING... IT IS
STILL MUCH TOO EARLY TO RULE OUT THE POSSIBILITY OF HURRICANE
CONDITIONS.
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      11/0900Z 31.7N  75.9W    75 KT
 12HR VT     11/1800Z 31.6N  76.0W    75 KT
 24HR VT     12/0600Z 31.6N  76.2W    75 KT
 36HR VT     12/1800Z 32.0N  76.5W    75 KT
 48HR VT     13/0600Z 32.6N  76.7W    75 KT
 72HR VT     14/0600Z 34.0N  76.5W    75 KT
 96HR VT     15/0600Z 36.5N  75.0W    50 KT
120HR VT     16/0600Z 39.5N  71.0W    40 KT
 
 
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