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| #10741 (Received by flhurricane at: 4:39 AM 28.Sep.2004) TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 36 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT TUE SEP 28 2004 THE CENTER REMAINS HARD TO LOCATE ON NIGHT-VIS AND INFRARED IMAGERY...AND SATELLITE FIXES FROM TAFB AND SAB ARE ABOUT 75 MILES APART. AMBIGUITIES FROM THE QUIKSCAT PASS AT 2142Z SHOWED THAT THE CIRCULATION OF LISA WAS ELONGATED ALONG A NNE/SSW AXIS...PERHAPS AS A RESULT OF THE PERSISTENT ASYMMETRY IN THE DEEP CONVECTION...WHICH IS CONFINED TO THE NORTHEAST QUADRANT OF THE CYCLONE. THE FIRST GOES-12 IMAGES AFTER ECLIPSE ALSO SUGGEST AN ELONGATED CIRCULATION. THE INTENSITY FOR THIS ADVISORY WILL BE HELD AT 35 KT...IN BETWEEN THE DVORAK T NUMBERS FROM TAFB AND SAB...AND THE INITIAL MOTION REMAINS 350/7. LISA IS MOVING SLOWLY THROUGH A WEAKNESS IN THE SUBTROPICAL RIDGE...AND THIS IS EXPECTED TO CONTINUE FOR THE NEXT 24 HOURS. AFTER THAT...MODEL GUIDANCE DIVERGES SOMEWHAT...WITH THE NOGAPS AND GFDL THE OUTLIERS TO THE WEST AND EAST RESPECTIVELY. THE GFDL SEEMS TO WANT TO MAKE LISA FOLLOW THE CONVECTION...AND THE APPARENT ELONGATION OF THE CIRCULATION MAKES ME THINK THAT THIS COULD BE STARTING TO OCCUR. MODEL GUIDANCE HAS BEEN CONSISTENTLY TRENDING EASTWARD OVER THE PAST FEW FORECAST CYCLES...AND SO I HAVE ADJUSTED THE OFFICIAL FORECAST EASTWARD OF AND FASTER THAN THE PREVIOUS ADVISORY. THE NEW FORECAST IS NEAR A CONSENSUS OF THE GFS...GFDL...AND UKMET MODELS. WATER VAPOR IMAGERY SHOWS A WELL-DEFINED UPPER-LEVEL TROUGH APPROACHING LISA FROM THE NORTHWEST...AND GLOBAL MODEL GUIDANCE SUGGESTS THAT THIS TROUGH WILL CUT OFF A SHORT DISTANCE WEST OF THE CYCLONE IN ABOUT 48 HOURS. IN THE SHORT RUN THIS WILL INCREASE THE SHEAR OVER LISA...BUT A MORE FAVORABLE UPPER PATTERN FOR INTENSIFICATION COULD DEVELOP AFTER THE UPPER LOW CUTS OFF AND MOVES SOUTHWESTWARD. THIS WOULD BE PARTICULARLY TRUE IF LISA TAKES THE MORE EASTWARD TRACK FORECAST BY THE GFDL. LATE IN THE FORECAST PERIOD LISA IS EXPECTED TO ENCOUNTER COOLER WATERS AND WEAKEN. THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS GUIDANCE...BUT CONSIDERABLY BELOW THAT OF THE GFDL. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 28/0900Z 23.1N 46.5W 35 KT 12HR VT 28/1800Z 24.3N 46.6W 35 KT 24HR VT 29/0600Z 26.3N 46.4W 40 KT 36HR VT 29/1800Z 28.7N 46.2W 45 KT 48HR VT 30/0600Z 31.0N 46.0W 55 KT 72HR VT 01/0600Z 35.0N 45.5W 60 KT 96HR VT 02/0600Z 38.0N 41.5W 60 KT 120HR VT 03/0600Z 39.0N 36.0W 50 KT |
