ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM 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 NNNN