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HURRICANE OLGA DISCUSSION NUMBER  11
NATIONAL WEATHER SERVICE MIAMI FL
4 AM EST TUE NOV 27 2001
 
OLGA HAS BEEN MAINTAINING A WELL-DEFINED EYE OVER THE PAST SEVERAL
HOURS...ALTHOUGH THE EYEWALL CONVECTION IS NOT QUITE AS SYMMETRIC AS
IT WAS A FEW HOURS AGO.  DVORAK T-NUMBERS FROM TAFB AND SAB
CORRESPOND TO AN INTENSITY OF ABOUT 75 KT...AND THAT REMAINS THE
OFFICIAL INTENSITY FOR THIS ADVISORY.  IT IS POSSIBLE THAT WITH THE
COOLISH WATER TEMPERATURES AND A PRESUMABLY STABLE BOUNDARY LAYER
THESE DVORAK ESTIMATES ARE A LITTLE HIGH.  THERE IS A
CONSIDERABLY-IMPROVED OUTFLOW PATTERN NOW COMPARED TO THIS TIME
YESTERDAY...WHEN THE UPPER WIND STRUCTURE WAS DECIDEDLY SUBTROPICAL.
 
OLGA HAS BEEN MEANDERING AND IS CURRENTLY EXECUTING A CYCLONIC LOOP
WITH A SEPARATE UPPER-LEVEL VORTICITY MAXIMUM CURRENTLY TO ITS
SOUTHEAST.  AS THESE TWO FEATURES INTERACT I EXPECT A SHORT-TERM
MOTION TO THE SOUTHWEST OR SOUTH FOR THE NEXT SEVERAL HOURS.  BEYOND
THAT...NEARLY ALL THE GUIDANCE SUGGESTS A SLOW NET EASTWARD DRIFT
OVER THE NEXT DAY OR TWO...BUT I AM NOT SOLD ON THE INITIALIZATION
OF THE GUIDANCE.  NEITHER THE AVN NOR THE UKMET SEEMS TO BE
CAPTURING THE FULL EXTENT OF THE OUTFLOW ON THE WEST SIDE OF THE
CYCLONE VISIBLE IN THE WATER-VAPOR IMAGERY.  THE OFFICIAL FORECAST
THEREFORE IS SOMEWHAT WEST OF THE GUIDANCE DURING THE FIRST HALF OF
THE FORECAST PERIOD...AND CALLS FOR LITTLE NET MOTION DURING THE
NEXT 36 HOURS.  BEYOND THAT...A SOUTHWESTWARD TRACK IS EXPECTED AS
HEIGHTS RISE NORTHWEST OF OLGA IN RESPONSE TO AN APPROACHING TROUGH
OVER THE CENTRAL U.S.

THE SSTS WOULD ARGUE THAT THERE SHOULD NOT BE MUCH MORE UPSIDE TO
THE INTENSITY OF OLGA...ALTHOUGH SOME MODEST ADDITIONAL
STRENGTHENING IS STILL POSSIBLE.  LATE IN THE PERIOD...WHEN OLGA IS
EXPECTED TO MOVE SOUTHWESTWARD...INCREASING SHEAR SHOULD MITIGATE
AGAINST INCREASING SSTS.  CLIMATOLOGICALLY..SOUTHWARD-MOVING
TROPICAL CYCLONES USUALLY WEAKEN.

FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     27/0900Z 32.5N  57.5W    75 KTS
12HR VT     27/1800Z 32.5N  57.5W    80 KTS
24HR VT     28/0600Z 32.5N  57.5W    80 KTS
36HR VT     28/1800Z 32.5N  57.5W    80 KTS
48HR VT     29/0600Z 31.5N  58.0W    75 KTS
72HR VT     30/0600Z 29.5N  59.5W    65 KTS
 
 
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