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| #9390 (Received by flhurricane at: 5:11 AM 21.Sep.2004) TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT TUE SEP 21 2004 LISA CONTINUES UNDER NORTHERLY SHEAR CAUSED BY THE OUTFLOW FROM KARL..WITH THE CENTER IN THE NORTHERN SIDE OF THE VERY COLD CONVECTIVE MASS. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM SAB...AND 45 KT FROM TAFB AND AFWA. THE INITIAL INTENSITY REMAINS 50 KT FOR THIS ADVISORY...AND THIS MIGHT BE A LITTLE CONSERVATIVE. THE INITIAL MOTION IS 280/10. LISA IS EMBEDDED IN A TROUGH EXTENDING FROM HURRICANE KARL THROUGH LISA TO A DISTURBANCE CENTERED NEAR 9.5N31W. EASTERLY LOW-LEVEL FLOW IS SEEN NORTHEAST OF THE TROUGH AXIS AND WEST TO NORTHWEST FLOW SOUTHWEST OF IT. THERE SEEM TO BE THREE POTENTIAL TRACK OPTIONS FOR LISA. FIRST...A CONTINUATION OF THE CURRENT WESTWARD MOTION AS KARL MOVES AWAY AND RIDGING DEVELOPS NORTH OF LISA. THIS IS FAVORED BY THE NHC98. SECOND...A TURN TO THE NORTHWEST AND NORTH IN THE WAKE OF KARL. THIS IS SUPPORTED BY THE NOGAPS AND THE UKMET. FINALLY...A TURN TO THE SOUTHWEST AS THE DISTURBANCE TO THE SOUTHEAST DEVELOPS. THIS IS SUPPORTED BY THE GFDL. THE TRACK FORECAST WILL FOLLOW THE PREVIOUS WESTWARD MOTION AS THERE IS CURRENTLY NO OBVIOUS SIGN THAT EITHER OF THE OTHER SCENARIOS ARE BEGINNING. ONE SMALL CHANGE IS TO INTRODUCE A NORTHWESTERLY MOTION AFTER 96 HR...AS LISA WOULD BE APPROACHING A WEAKNESS IN THE RIDGE TO THE NORTH BY THAT TIME. THIS IS ANOTHER LOW CONFIDENCE FORECAST. THE INTENSITY FORECAST IS EVEN LOWER CONFIDENCE. LISA IS A SMALL SYSTEM BETWEEN TWO LARGER ONES...AND THERE IS A CHANCE THAT IT COULD GET SWALLOWED...PARTICULARLY BY THE DISTURBANCE TO THE SOUTHEAST. IF THAT DOES NOT HAPPEN... LARGE-SCALE MODELS ALL FORECAST SIGNIFICANT NORTHEASTERLY SHEAR ALONG THE FORECAST TRACK IN 48-72 HR...WHICH COULD CONSIDERABLY DAMAGE LISA. THE SHIPS AND GFDL BOTH SLOWLY STRENGTHEN LISA IN SPITE OF THE SHEAR...AND THE OFFICIAL FORECAST FOLLOWS THE SHIPS GUIDANCE. HOWEVER...THERE IS A CHANCE LISA MIGHT NOT SURVIVE FOR 120 HR. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 21/0900Z 14.0N 38.9W 50 KT 12HR VT 21/1800Z 14.3N 40.3W 50 KT 24HR VT 22/0600Z 14.9N 42.0W 50 KT 36HR VT 22/1800Z 15.4N 43.6W 50 KT 48HR VT 23/0600Z 15.8N 45.2W 55 KT 72HR VT 24/0600Z 16.0N 47.5W 60 KT 96HR VT 25/0600Z 16.1N 50.0W 65 KT 120HR VT 26/0600Z 17.5N 51.5W 65 KT |
