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| #378057 (Received by flhurricane at: 4:37 PM 22.Sep.2010) TCDAT4 TROPICAL STORM LISA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL142010 500 PM AST WED SEP 22 2010 LISA HAS A ROBUST CIRCULATION...BUT ALL THE DEEP CONVECTION REMAINS LIMITED TO NEAR THE CENTER. THE CONVECTIVE STRUCTURE HAS CHANGED LITTLE OVER THE PAST FEW HOUR HOURS...SO THE INITIAL INTENSITY IS KEPT AT 40 KT. ALTHOUGH VERTICAL SHEAR IS LIGHT...THE CYCLONE IS SURROUNDED BY MID-LEVEL DRY AIR AND IS LOCATED OVER AN AREA WHERE THE OCEAN HEAT CONTENT IS RATHER LOW. THEREFORE ONLY A LITTLE STRENGTHENING IS INDICATED IN THE OFFICIAL FORECAST DURING THE NEXT 48 HOURS...WHEN CONDITIONS WILL BE MOST FAVORABLE. WEAKENING IS EXPECTED FROM DAYS 3-5 AS 30-40 KT OF WEST-SOUTHWESTERLY SHEAR DEVELOPS OVER THE CYCLONE. THE FORECAST INDICATES LISA BECOMING A TROPICAL DEPRESSION BY DAY 5...BUT IT IS POSSIBLE THAT IT COULD HAVE DEGENERATED TO A REMNANT LOW OR TROUGH BY THAT TIME. LISA HAS BEEN MEANDERING ALL DAY...AND THE ESTIMATED INITIAL MOTION IS 090/3 BASED ON A 12-18 HOUR AVERAGE. MODEL GUIDANCE SUGGESTS THAT LISA COULD DRIFT A LITTLE FARTHER EASTWARD OR SOUTHEASTWARD DURING THE NEXT 12-24 HOURS IN WEAK STEERING FLOW...BUT IT IS EXPECTED TO PICK UP SOME SPEED AND MOVE NORTHWESTWARD BY 48 HOURS AS A MID-LEVEL RIDGE OVER AFRICA BUILDS WESTWARD. THE TRACK GUIDANCE HAS SHIFTED TO THE NORTH...AND THE OFFICIAL FORECAST IS ABOUT 2 DEGREES FARTHER NORTH THAN THE PREVIOUS ONE BY DAY 5. FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 17.7N 30.2W 40 KT 12HR VT 23/0600Z 17.6N 29.9W 40 KT 24HR VT 23/1800Z 17.8N 29.9W 45 KT 36HR VT 24/0600Z 18.1N 30.6W 45 KT 48HR VT 24/1800Z 18.6N 31.2W 50 KT 72HR VT 25/1800Z 20.1N 32.7W 45 KT 96HR VT 26/1800Z 22.0N 35.0W 40 KT 120HR VT 27/1800Z 24.0N 38.0W 30 KT $$ FORECASTER BERG |
