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TROPICAL STORM OLGA DISCUSSION NUMBER  21
NATIONAL WEATHER SERVICE MIAMI FL
4 PM EST THU NOV 29 2001
 
THE CENTER OF OLGA HAS BECOME EXPOSED TO THE NORTH OF THE
CONVECTION AS ANALYSES FROM CIMSS AT THE UNIVERSITY OF WISCONSIN
CONTINUE TO SHOW 20-30 KT OF VERTICAL SHEAR OVER THE SYSTEM.
SHIP HBEB REPORTED 34 KT WINDS AND A 1001.2 MB PRESSURE ABOUT
45 NM SOUTHWEST OF THE CENTER AT 18Z...AND THE SHIP WAS LIKELY NOT
IN THE AREA OF STRONGEST WINDS.  SATELLITE INTENSITY ESTIMATES
ARE 55 KT...SO THAT IS THE INITIAL INTENSITY FOR THIS ADVISORY.

THE INITIAL MOTION IS NOW 235/17.  THERE IS LITTLE CHANGE IN
THE SYNOPTIC PATTERN DRIVING OLGA...AS THE SYSTEM IS MOVING
SOUTHWESTWARD AROUND THE SOUTHEAST SIDE OF A DEEP-LAYER RIDGE
OVER THE SOUTHEASTERN U. S. AND THE ADJACENT ATLANTIC.  THIS
RIDGE SHOULD WEAKEN AFTER 24-36 HR AS A TROUGH AND ASSOCIATED
FRONTAL SYSTEM MOVE TOWARD THE U. S. EAST COAST.  THIS PATTERN
SHOULD ALLOW OLGA TO MOVES SOUTHWESTWARD FOR 24 HR OR SO...THEN
GRADUALLY SLOW DOWN AND TURN WESTWARD.  THE TRACK GUIDANCE MODELS
ARE IN GOOD AGREEMENT WITH THIS SCENARIO...WITH THE MAJOR
DIFFERENCES BEING IN SPEED.  THE OFFICIAL TRACK FORECAST IS
SIMILAR TOO BUT CONSIDERABLY FASTER THAN THE PREVIOUS PACKAGE...
BASED ON THE CURRENT MOTION AND ADJUSTING THE FORECAST CLOSER TO
THE FASTER MODEL GUIDANCE.

LARGE-SCALE MODELS INDICATE THE CURRENT VERTICAL SHEAR SHOULD
CONTINUE FOR AT LEAST 36 HR...AND OLGA SHOULD CONTINUE TO STEADILY
WEAKEN DURING THAT TIME.  SOME DECREASE IN THE SHEAR MAY OCCUR
IN ABOUT 36-60 HR...BUT THIS IS LIKELY TO BE SHORT-LIVED AND OLGA
WILL LIKELY BE TOO DISORGANIZED TO TAKE ADVANTAGE OF THE DECREASE.
THUS...THE CYCLONE IS FORECAST TO BE DISSIPATING IN 72 HR.

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     29/2100Z 26.9N  62.6W    55 KTS
12HR VT     30/0600Z 25.7N  64.8W    50 KTS
24HR VT     30/1800Z 24.8N  67.5W    45 KTS
36HR VT     01/0600Z 24.5N  70.1W    40 KTS
48HR VT     01/1800Z 24.5N  72.2W    35 KTS
72HR VT     02/1800Z 24.5N  75.0W    25 KTS...DISSIPATING
 
 
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