[NCEP Logo] HOME ARCHIVES FORECASTS IMAGERY ABOUT TPC RECONNAISSANCE

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HURRICANE OLGA DISCUSSION NUMBER  16
NATIONAL WEATHER SERVICE MIAMI FL
10 AM EST WED NOV 28 2001

OLGA STILL HAS A WELL-DEFINED EYE THIS MORNING.  HOWEVER...THE
EYEWALL CONVECTION HAS WEAKENED SOMEWHAT AND BECOME ASYMMETRIC.
SATELLITE INTENSITY ESTIMATES FROM TAFB...SAB...AND AFWA REMAIN
77 KT...SO THE INITIAL INTENSITY REMAINS 75 KT ON THIS ADVISORY.

OLGA HAS BEEN MOVING SOUTHWEST FOR THE PAST FEW HOURS WITH A
SHORT-TERM MOTION OF 235/4.  IT IS NOT YET CLEAR WHETHER THIS IS
THE START OF THE MOTION LONG FORECAST BY THE LARGE-SCALE MODELS OR
THE START OF ANOTHER LOOP.  HOWEVER...WATER VAPOR IMAGERY SUGGESTS 
MID/UPPER LEVEL RIDGING BUILDING TO THE WEST AND NORTHWEST OF THE
CYCLONE...WHICH SHOULD START OLGA MOVING SOUTHWESTWARD WITHIN THE
NEXT 12-24 HR EVEN IF THE CURRENT MOTION IS ANOTHER LOOP.  MODEL
GUIDANCE IS NOW FAIRLY TIGHTLY CLUSTERED AROUND A SOUTHWESTWARD
MOTION...AND THE OFFICIAL TRACK FORECAST IS ALONG THE NORTHERN
SIDE OF THE GUIDANCE.
 
WATER VAPOR IMAGERY INDICATES THAT THE BUILDING RIDGE TO THE WEST
IS INCREASING THE NORTHERLY UPPER-LEVEL FLOW TO THE NORTH OF OLGA...
AND THAT THIS FLOW IS WORKING ITS WAY TOWARD THE HURRICANE.  LARGE-
SCALE MODELS INDICATE THIS INCREASING VERTICAL SHEAR SHOULD AFFECT
OLGA IN THE NEXT 6-24 HR...AND THE INTENSITY FORECAST THUS CALLS
FOR WEAKENING.  THINGS GET A LITTLE TRICKIER BEYOND 36 HR. 
CLIMATOLOGY INDICATES THAT MOST ATLANTIC TROPICAL CYCLONES THAT
MOVE SOUTHWESTWARD WEAKEN...OR AT BEST HOLD THEIR OWN.  ON THIS
BASIS...AND THE GOOD CHANCE THAT OLGA'S SMALL CORE WILL GET
DISRUPTED BY THE SHEAR...THE INTENSITY FORECAST CALLS FOR CONTINUED
WEAKENING.  HOWEVER...THE FORECAST TRACK TAKES THE STORM TOWARD
WARMER WATER... AND LARGE-SCALE MODELS INDICATE AT LEAST THE
POSSIBILITY THAT THE UPPER-LEVEL COULD RE-FORM IN IN A POSITION TO
DECREASE THE VERTICAL SHEAR.  SHOULD THAT HAPPEN...OLGA MAY WEAKEN
MORE SLOWLY THAN CURRENTLY FORECAST.
 
FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     28/1500Z 32.2N  56.4W    75 KTS
12HR VT     29/0000Z 32.0N  56.8W    70 KTS
24HR VT     29/1200Z 31.5N  57.7W    65 KTS
36HR VT     30/0000Z 30.6N  59.2W    60 KTS
48HR VT     30/1200Z 29.6N  60.9W    55 KTS
72HR VT     01/1200Z 28.5N  64.0W    45 KTS
 
 
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