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| #10478 (Received by flhurricane at: 11:17 PM 26.Sep.2004) TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 31 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN SEP 26 2004 LISA CONTINUES TO PRODUCE SPORADIC BURSTS OF DEEP CONVECTION ON THE NORTHEAST SIDE OF AN OCCASIONALLY-EXPOSED LOW-LEVEL CENTER. A 2337 UTC SSMI MICROWAVE PASS SHOWED THAT THE CYCLONE IS A LITTLE FARTHER SOUTH THAN THOUGHT AND HAS BEEN MOVING RATHER SLOWLY. DVORAK INTENSITY ESTIMATES HAVE NOT CHANGED WITH A SHEARED TROPICAL CYCLONE PATTERN PRESENT SO THE INITIAL INTENSITY REMAINS 45 KT. MICROWAVE FIXES INDICATE THE STORM HAS BEEN MOVING GENERALLY TO THE NORTH AROUND 5 KT FOR THE PAST 6-12 HOURS. THE OFFICIAL FORECAST IS SHIFTED A LITTLE TO THE RIGHT IN THE NEAR-TERM TO ACCOUNT FOR THE SLOWER AND MORE NORTHERLY MOTION.A MORE NORTHWESTERLY OR NORTH-NORTHWESTERLY MOTION SHOULD COMMENCE SOON DUE TO A MIDDLE- LEVEL RIDGE BUILDING TO THE NORTH AND NORTHEAST OF LISA. THE FORECAST BEYOND 2 DAYS IS RATHER UNCERTAIN WITH CONSIDERABLE SPREAD IN MODEL GUIDANCE. THERE SEEMS TO BE TWO CLUSTERS OF SOLUTIONS EMERGING. THE UKMET/GFS MODELS WANT TO RECURVE LISA THRU A BREAK IN THE SUBTROPICAL RIDGE ALONG 50W. THE OTHER CLUSTER COMPOSED OF THE NOGAPS/GFDN/GFDL SUGGESTS THAT THE STORM WILL NOT RECURVE AND WILL INSTEAD TAKE A WESTERLY TURN UNDER A BUILDING RIDGE OVER THE WEST-CENTRAL ATLANTIC. IF THE CURRENT SLOW MOTION CONTINUES THE MORE WESTERLY MOTION COULD BE CORRECT AS THE RIDGE WOULD HAVE MORE TIME TO BUILD TO THE NORTH OF LISA. WITH SO MUCH UNCERTAINTY...THE OFFICIAL FORECAST WILL SLOW THE MOTION CONSIDERABLY IN THE MEDIUM- RANGE BETWEEN THE TWO CLUSTERS. IN ADDITION TO ABOUT 15-20 KT OF SOUTHWESTERLY SHEAR...LISA HAS BEEN MOVING OVER THE COOL WAKE OF KARL...FURTHER HINDERING ITS DEVELOPMENT. LITTLE CHANGE IN STRENGTH IS LIKELY UNTIL AFTER 24 HOURS WHEN THE STORM MOVES OVER WARMER WATER WITH ABOUT THE SAME AMOUNT OF SHEAR. GLOBAL MODEL GUIDANCE SUGGESTS THAT THE SHEAR WILL DECREASE IN TWO OR THREE DAYS AS AN UPPER TROUGH CUTS OFF FROM THE MID-LATITUDES WEST OF LISA. THIS PATTERN WOULD BE SLIGHTLY MORE FAVORABLE FOR INTENSIFICATION OVER WARM WATER NEAR 28C BUT THERE IS CONSIDERABLY UNCERTAINTY ON WHERE THE STORM WILL BE AT THAT POINT. WITH SO MUCH AMBUIGUITY PRESENT THERE IS NO CHANGE TO THE PREVIOUS INTENSITY FORECAST. FORECASTER BLAKE/STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 27/0300Z 19.7N 46.1W 45 KT 12HR VT 27/1200Z 20.8N 46.4W 45 KT 24HR VT 28/0000Z 22.4N 47.4W 45 KT 36HR VT 28/1200Z 24.0N 48.4W 50 KT 48HR VT 29/0000Z 25.4N 49.1W 55 KT 72HR VT 30/0000Z 27.5N 50.0W 65 KT 96HR VT 01/0000Z 29.0N 50.5W 65 KT 120HR VT 02/0000Z 31.0N 51.0W 65 KT |
