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| #9585 (Received by flhurricane at: 4:44 PM 22.Sep.2004) TCDAT3 TROPICAL STORM LISA DISCUSSION NUMBER 14 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 PM EDT WED SEP 22 2004 A BURST OF CONVECTION EARLY THIS AFTERNOON OBSCURED THE CENTER...BUT THAT CONVECTION IS NOW FADING AND BEING BLOWN OFF BY EASTERLY SHEARING WINDS ALOFT. THE INITIAL INTENSITY IS HELD AT 45 KT IN ACCORD WITH AN EARLIER QUIKSCAT PASS AND A DVORAK CLASSIFICATION OF 3.0 FROM TAFB. THE INTENSITY FORECAST IS COMPLICATED BY THE PRESENCE OF A LARGE TROPICAL DISTURBANCE ONLY 300 MILES TO THE EAST OF LISA. THE UPPER-FLOW OVER THIS LATTER FEATURE IS MORE FAVORABLE FOR DEVELOPMENT THAN THE SHEARING FLOW OVER LISA...AND IT IS HARD TO IMAGINE BOTH OF THESE SYSTEMS BEING TROPICAL CYCLONES IN 48 HOURS. IT IS QUITE POSSIBLE THAT LISA WILL END UP BEING ABSORBED BY THE EASTERN DISTURBANCE WITHIN A COUPLE OF DAYS. SHOULD IT SURVIVE...UPPER-LEVEL WINDS COULD BECOME MORE FAVORABLE IN 2-3 DAYS AND THE OFFICIAL FORECAST SHOWS SOME INTENSIFICATION FOLLOWING THE SHIPS AND GFDL GUIDANCE. NEAR THE END OF THE FORECAST PERIOD HOWEVER...A STRONG 200 MB TROUGH IS EXPECTED TO DIG DEEP INTO THE CENTRAL TROPICAL ATLANTIC...WHICH WOULD INCREASE THE SHEAR OVER WHICHEVER OF LISA OR THE DISTURBANCE STILL EXISTS. THE INITIAL MOTION ESTIMATE IS 240/5. LISA AND THE DISTURBANCE ARE BEGINNING TO REVOLVE AROUND A COMMON CENTER OF ROTATION SOUTH OF A NARROW RIDGE TO THE SOUTH OF KARL. THE GFS SHOWS THE STRONGEST INTERACTION BETWEEN THE TWO TROPICAL SYSTEMS...TAKING LISA SOUTHWARD AND EASTWARD BEFORE DISSIPATING IT. THE GFDL... NOGAPS...AND UKMET MERELY CONTINUE A SLOW SOUTHWESTWARD MOTION FOR ABOUT TWO DAYS...KEEPING LISA AS THE STRONGER SYSTEM. BY THE TIME THIS INTERACTION IS OVER...THE STRONG UPPER-LEVEL TROUGH NOTED ABOVE IS EXPECTED TO IMPART MORE OF A NORTHWARD MOTION BY DAYS 4 AND 5. THE OFFICIAL FORECAST IS IN BEST AGREEMENT WITH THE GFDL GUIDANCE. FORECASTER FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 13.7N 41.9W 45 KT 12HR VT 23/0600Z 13.4N 42.3W 45 KT 24HR VT 23/1800Z 13.0N 42.8W 45 KT 36HR VT 24/0600Z 12.7N 43.5W 45 KT 48HR VT 24/1800Z 12.5N 44.5W 45 KT 72HR VT 25/1800Z 14.0N 45.5W 55 KT 96HR VT 26/1800Z 17.0N 46.5W 65 KT 120HR VT 27/1800Z 20.0N 48.0W 65 KT |
