ZCZC MIATCDAT2 ALL TTAA00 KNHC DDHHMM HURRICANE OLGA DISCUSSION NUMBER 15 NATIONAL WEATHER SERVICE MIAMI FL 4 AM EST WED NOV 28 2001 DVORAK-BASED INTENSITY ESTIMATES FROM TAFB AND SAB ARE T4.5... CORRESPONDING TO 77 KT. THE LATEST OBJECTIVE DVORAK ESTIMATES ARE A LITTLE LOWER AT T4.3...SO THE INITIAL INTENSITY IS SET TO 75 KT FOR THIS ADVISORY. SATELLITE IMAGERY SHOWS THAT THE OUTFLOW PATTERN HAS DETERIORATED SOMEWHAT OVER THE PAST 24 HOURS. OLGA IS CURRENTLY IN A LOW-SHEAR UPPER ENVIRONMENT WITHIN A BROAD CYCLONIC CIRCULATION. HOWEVER...THIS BROAD UPPER PATTERN IS FORECAST TO EVOLVE INTO A SHARP AND ELONGATED TROUGH THAT SHOULD EXPOSE THE HURRICANE TO INCREASING SHEAR WITHIN 36 HOURS. BOTH THE UKMET AND AVIATION MODELS WEAKEN OLGA TO A DEPRESSION OR LESS WITHIN 72 HOURS. THE SHIPS MODEL MAINTAINS A 55 KT STORM BY 72 HOURS...BUT I BELIEVE IT DOES NOT HAVE A GOOD HANDLE ON THE SHEAR...WHILE THE GFDL BRINGS OLGA DOWN TO 30 KT. ALTHOUGH OLGAS OVERALL CIRCULATION IS STILL LARGE...THE AREA COVERED BY STRONG WINDS IS RATHER SMALL...SO THE MAXIMUM WINDS COULD DROP QUICKLY ONCE THE INNER CORE BEGINS TO COLLAPSE. THE OFFICIAL FORECAST CALLS FOR MORE WEAKENING THAN THE PREVIOUS FORECAST...BUT IS NOT AS RAPID AS THE GLOBAL MODELS OR GFDL. AFTER COMPLETING A RELATIVELY LARGE CYCLONIC LOOP THIS AFTERNOON... OLGA IS NOW EXECUTING A SECOND...MUCH TIGHTER LOOP. THIS SUGGESTS THAT THE BINARY INTERACTIONS WITH VORTICITY CENTERS IN ITS IMMEDIATE ENVIRONMENT ARE ENDING. THE NET EFFECT OF ALL THIS LOOPING IS AN OFFICIALLY STATIONARY INITIAL MOTION. THE TROPICAL CYCLONE IS EMBEDDED WITHIN A LARGER-SCALE DEEP-LAYER CYCLONIC CIRCULATION THAT IS PRETTY MUCH ISOLATED FROM THE MAIN BELT OF WESTERLIES. THIS LARGER CIRCULATION IS EXPECTED TO SHIFT SLOWLY SOUTHWESTWARD OVER THE NEXT FEW DAYS...AND BRING OLGA WITH IT. THERE IS NOW GOOD AGREEMENT AMONG THE UKMET...AVIATION...AND GFDL MODELS. THE OFFICIAL TRACK FORECAST SHOWS THE SOUTHWESTWARD MOTION COMMENCING IN A DAY OR SO...AND IS AGAIN FASTER THAN THE PREVIOUS OFFICIAL FORECAST...BUT STILL SLOWER THAN THE GLOBAL MODEL CONSENSUS. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 28/0900Z 32.6N 55.8W 75 KTS 12HR VT 28/1800Z 32.5N 56.0W 70 KTS 24HR VT 29/0600Z 32.5N 56.0W 65 KTS 36HR VT 29/1800Z 31.0N 57.5W 60 KTS 48HR VT 30/0600Z 29.5N 59.5W 55 KTS 72HR VT 01/0600Z 28.0N 63.0W 45 KTS NNNN