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#378435 (Received by flhurricane at: 10:41 AM 24.Sep.2010) TCDAT4 TROPICAL STORM LISA DISCUSSION NUMBER 15 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL142010 1100 AM AST FRI SEP 24 2010 SATELLITE IMAGERY DURING THE PAST 6 HOURS INDICATES THAT DEEP CONVECTION HAS CONTINUED TO DEVELOP AND NOW WRAPS ABOUT THREE-FOURTHS OF THE WAY AROUND THE CENTER. CLOUD TOPS HAVE COOLED TO NEAR -80C JUST NORTH OF THE CENTER...AND VISIBLE AND MICROWAVE IMAGERY HAVE BEEN HINTING OF A BANDING-EYE FEATURE TRYING TO FORM. THE INITIAL INTENSITY OF 40 KT IS BASED ON A BLEND OF SATELLITE INTENSITY ESTIMATES OF T2.5/35 KT FROM TAFB...TAFB AODT ESTIMATES OF T3.4/53 KT...AND UW-CIMSS 3-HR AVERAGE ADT ESTIMATES OF T3.4/53 KT. A 24/1146Z ASCAT OVERPASS SHOWED 33-KT WINDS EAST OF THE CENTER...BUT THERE IS PROBABLY SOME UNDER SAMPLING OCCURRING DUE TO THE VERY SMALL SIZE OF THE INNER-CORE CIRCULATION. THEREFORE...IT IS POSSIBLE THAT LISA COULD BE A LITTLE STRONGER THAN ANALYZED. SATELLITE MICROWAVE AND CONVENTIONAL FIXES INDICATE LISA IS NOW MOVING AT ABOUT 360/06. THE GENERAL MOTION SHOULD BE NORTHWARD FOR THE NEXT 24-36 HOURS AS LISA MOVES AROUND THE WESTERN PERIPHERY OF THE SAHARAN SUBTROPICAL RIDGE. AS LISA MOVES OVER COLDER WATER AND ENCOUNTERS MODERATE TO STRONG WESTERLY SHEAR AHEAD OF A SHORTWAVE TROUGH...THE LOW-LEVEL AND UPPER-LEVEL CIRCULATIONS ARE EXPECTED TO DECOUPLE. AS A RESULT... THE LOW-LEVEL CIRCULATION IS FORECAST TO MOVE NORTH-NORTHWESTWARD OR NORTHWESTWARD AS A REMNANT LOW PRESSURE SYSTEM IN 48-72 HOURS. THE NHC FORECAST TRACK IS ADJUSTED RIGHTWARD TOWARD THE MODEL CONSENSUS...BUT IS STILL ALONG THE LEFT SIDE OF THE GUIDANCE ENVELOPE. WHILE IT IS POSSIBLE THAT LISA COULD INTENSIFY MORE THAN FORECAST BASED ON RECENT SATELLITE TRENDS...THIS CYCLONE HAS HAD A LONG HISTORY OF APPEARING TO GET STRONGER...ONLY TO HAVE THE CYCLONE INGEST DRY AIR NEARBY THAT HAS CAUSED THE INNER-CORE CONVECTION TO WEAKEN AND SOMETIMES EVEN DISSIPATE. BY 24 HOURS...LISA IS FORECAST TO MOVE OVER COOLER SSTS BELOW 26C AND ENCOUNTER VERTICAL WIND SHEAR OF 20-40 KT. THESE NEGATIVE FACTORS SHOULD INDUCE STEADY WEAKENING AND POSSIBLE DISSIPATION IN 96-120 HOURS. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A LITTLE LOWER THAN ALL OF THE OBJECTIVE INTENSITY FORECAST GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 24/1500Z 18.9N 27.8W 40 KT 12HR VT 25/0000Z 19.8N 27.9W 40 KT 24HR VT 25/1200Z 21.2N 28.2W 35 KT 36HR VT 26/0000Z 22.9N 28.6W 35 KT 48HR VT 26/1200Z 24.3N 29.0W 30 KT 72HR VT 27/1200Z 26.5N 29.8W 25 KT...POST-TROP/REMNT LOW 96HR VT 28/1200Z 28.0N 30.5W 20 KT...POST-TROP/REMNT LOW 120HR VT 29/1200Z...DISSIPATED $$ FORECASTER STEWART |