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TROPICAL DEPRESSION OLGA DISCUSSION NUMBER  27
NATIONAL WEATHER SERVICE MIAMI FL
5 AM AST SAT DEC 01 2001

OLGA CONTINUES TO GENERATE CONVECTION OVER THE EASTERN QUADRANT...
ALTHOUGH THE COVERAGE AND INTENSITY HAS DECREASED OVER THE PAST
6 HR.  THE CONVECTION ALSO SEEMS TO BE FURTHER AWAY FROM THE CENTER.
THE MAXIMUM INTENSITY REMAINS 30 KT BASED ON SATELLITE ESTIMATES
FROM TAFB AND AFWA...AN EARLIER SSM/I OVERPASS SHOWING 30 KT WINDS
IN THE NORTHERN SEMICIRCLE...AND REPORTS FROM DRIFTING BUOY 41647.

THE PARTIALLY-EXPOSED CENTER OF OLGA IS A BIT DIFFICULT TO FIND...
AND SMALL LOW CLOUD SWIRLS ROTATING AROUND THE LARGER-SCALE CENTER
ARE COMPLICATING THE ISSUE.  THE BEST ESTIMATE OF THE INITIAL MOTION 
IS 240/7...AND THIS MIGHT BE A TRIFLE FAST.  SATELLITE IMAGERY AND
SURFACE DATA SHOW LOW/MID LEVEL RIDGING NORTH OF OLGA...WITH WATER
VAPOR IMAGERY INDICATING AN UPPER LEVEL LOW NEAR 27N 66W.  SINCE
OLGA IS SIGNIFICANTLY SHEARED...IT SHOULD BE STEERED GENERALLY
WESTWARD BY THE FLOW AROUND THE LOW/MID LEVEL RIDGE.  THE OFFICIAL
FORECAST TRACK IS SIMILAR TO...BUT A LITTLE SOUTH OF...THE PREVIOUS
FORECAST...CALLING FOR THE CURRENT WEST-SOUTHWESTWARD MOTION TO
BECOME WESTWARD BY 24 HR AND WEST-NORTHWESTWARD BY 48 HR.  IT SHOULD
BE NOTED THAT THE FORECAST TRACK IS ALONG THE SOUTH EDGE OF THE
GUIDANCE.

ANALYSES OF VERTICAL SHEAR AND SHEAR TENDENCY FROM CIMSS AT THE
UNIVERSITY OF WISCONSIN INDICATES THAT THE SHEAR OVER OLGA HAS
DECREASED TO ABOUT 20 KT.  SOME FURTHER DECREASE IN SHEAR IS
POSSIBLE IN THE NEXT 24-36 HR AS THE UPPER LOW APPROACHES.
HOWEVER...OLGA WILL LIKELY BE LOCATED ON WHAT IS NORMALLY THE SIDE
OF THE UPPER LOW DOMINATED BY SUBSIDENCE...A LESS THAN IDEAL
LOCATION.  THUS...IF THE DECREASE IN SHEAR HAS ANY EFFECT...IT
MOST LIKELY WOULD ONLY LENGTHEN THE LIFE OF OLGA AS A DEPRESSION BY
12-24 HR FROM WHAT IS CURRENTLY FORECAST.  LARGE-SCALE MODELS
INDICATE STRONGER WESTERLY FLOW IMPACTING OLGA FROM 48 HR ONWARD...
AND THAT SHOULD FINISH THE CYCLONE OFF IF IT HAS NOT YET ALREADY
DIED.

 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     01/0900Z 22.9N  68.7W    30 KTS
12HR VT     01/1800Z 22.6N  69.6W    25 KTS...DISSIPATING
24HR VT     02/0600Z 22.6N  71.0W    25 KTS...REMNANT LOW
36HR VT     02/1800Z 22.7N  72.2W    25 KTS...REMNANT LOW
48HR VT     03/0600Z 22.9N  73.3W    20 KTS...REMNANT LOW
72HR VT     04/0600Z 23.5N  75.5W    20 KTS...REMNANT LOW
 
 
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