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| #91293 (Received by flhurricane at: 11:03 PM 12.Jun.2006) TCDAT1 TROPICAL STORM ALBERTO DISCUSSION NUMBER 12 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL012006 1100 PM EDT MON JUN 12 2006 AN AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT MEASURED 68-KT WINDS AT 700 MB IN THE NORTHEAST QUADRANT JUST NORTHWEST OF CEDAR KEY FLORDIA... WHICH WAS IN AN AREA OF 64+ KT DOPPELR VELOCITY DATA FROM TAMPA BAY AND TALLAHASSEE. THESE WIND REPORTS WERE IN AREAS OF CONVECTIVE BANDING WITH REFLECTIVITIES OF AT LEAST 40 DBZ...SO USING A 90 PERCENT REDUCTION FACTOR SEEMS APPROPROPRIATE...WHICH MEANS THAT ALBERTO REMAINS A 60-KT TROPICAL STORM. THE CENTRAL PRESSURE OF 995 MB IS BASED ON EARLIER RECON DROPSONDE REPORT OF 996 MB WITH A 15-KT SURFACE WIND...AND NOAA BUOY 42036...LOCATED NORTHEAST OF THE CENTER... REPORTING 997.2 MB PRESSURE AT 13/02Z. THE INITIAL MOTION ESTIMATE REMAINS 040/09 KT. UPPER-AIR DATA THIS EVENING INDICATE A NARROW 850-500 MB RIDGE EXTENDING NORTHWESTWARD AHEAD OF ALBERTO ACROSS SOUTHEASTERN GEORGIA. THIS FEATURE IS EXPECTED TO NUDGE THE CYCLONE A LITTLE TO THE LEFT OF ITS CURRENT MOTION...BEFORE THE BEING TURNED BACK TO THE NORTHEAST AHEAD OF A DIGGING MID-LEVEL SHORTWAVE CURRENTLY LOCATED ACROSS THE TENNESSEE AND MISSOURI VALLEYS. THE OFFICIAL FORECAST TRACK REMAINS NEAR THE RIGHT OR EAST SIDE OF THE MODEL GUIDANCE ENVELOPE...AND IS A LITTRL FATER THAN THE PREVIOSU ADVISORY AFTER ALBERTO BECOMES EXTRATROPICAL. IT IS POSSIBLE THAT THE INCREASING NORTHWESTERLY MID-LEVEL FLOW MAY FORCE THE EXTRATROPICAL LOW CLOSER TO THE CAROLINA COASTS BY 48 HOURS...RESULTING IN AN OVER WATER EXTRATROPICAL GALE AREA. SOME SHALLOW CONVECTION HAS BEEN DEVELOPING AROUND THE LOW-LEVEL CENTER DURING THE PAST FEW HOURS. WHILE GULF WATER TEMPERATURES ARE ONLY AROUND 79-80F AHEAD OF ALBERTO... THE 00Z UPPER-AIR SOUNDING FROM TAMPA INDICATES THAT THE ATMOPSHERE AHEAD OF THE CYCLONE AHS BECOME MORE UNSTABLE SINCE 12Z THIS MORNING. SINCE THERE IS AVAILABLE INSTABOLILY TO SUPPORT THE REGENERATION OF SIGNIFICANT CONVECTION LATER TONIGHT AND TUESDAY MORNING... A FORECAST OF ALBERTO POSSIBLY REACHING HURRICANE STRENGTH BEFORE LANDFALL APPEARS TO STILL BE IN ORDER. IN ADDITION TO HEAVY RAINS...THE MAIN HAZARD ASSOCIATED WITH ALBERTO WILL LIKELY BE STORM SURGE FLOODING...WHICH COULD BE 8-10 FEET ABOVE NORMAL TIDE LEVELS EVEN FOR A STRONG TROPICAL STORM IN THIS AREA. IT IS...HOWEVER...IMPOSSIBLE TO SPECIFY EXACTLY WHICH LOCATIONS WILL EXPERIENCE THE GREATEST STORM SURGE FLOODING BECAUSE THIS WILL DEPEND UPON THE PRECISE TRACK AND WIND FIELD NEAR LANDFALL. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 13/0300Z 28.4N 84.6W 60 KT 12HR VT 13/1200Z 29.5N 83.7W 65 KT 24HR VT 14/0000Z 31.1N 82.5W 40 KT...INLAND 36HR VT 14/1200Z 33.1N 80.6W 30 KT...INLAND 48HR VT 15/0000Z 35.0N 77.2W 30 KT...INLAND 72HR VT 16/0000Z 39.5N 68.0W 40 KT...EXTRATROPICAL 96HR VT 17/0000Z 44.0N 60.0W 40 KT...EXTRATROPICAL 120HR VT 18/0000Z 49.5N 50.0W 40 KT...EXTRATROPICAL |
