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| #39262 (Received by flhurricane at: 5:03 AM 13.Aug.2005) TCDAT4 TROPICAL STORM IRENE DISCUSSION NUMBER 35 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT SAT AUG 13 2005 A DEEP BURST OF CONVECTION BEGAN AT ABOUT 04Z... AND THE COLDEST CONVECTIVE TOPS REMAIN LESS THAN -70 DEGREES CELSIUS. AN AIR FORCE RECONNAISSANCE AIRCRAFT LOCATED THE CIRCULATION CENTER JUST NORTH OF THIS DEEP CONVECTION... AND MAXIMUM 850 MB FLIGHT LEVEL WINDS OF 69 KT WITHIN IT... WHICH CORRESPONDS TO SURFACE WINDS OF 55 KT. THE AIRCRAFT ALSO MEASURED A MINIMUM CENTRAL PRESSURE A BIT HIGHER THAN PREVIOUSLY THOUGHT... 997 MB. DVORAK DATA T NUMBERS ARE UNANIMOUSLY 3.5/55 KT. WHILE THERE ARE NO HARD NUMBERS TO SUPPORT MAINTAINING THE INTENSITY AT 60 KT... I WILL DO SO BASED ON THE CONVECTIVE ORGANIZATION NEAR THE CIRCULATION CENTER. AIRCRAFT FIXES DURING THE PAST FEW HOURS INDICATE THAT IRENE IS STILL MOVING NORTHWESTWARD... BUT A LITTLE FARTHER EAST THAN THE PREVIOUS FORECAST TRACK... WITH INITIAL MOTION NOW ESTIMATED AT 320/9. IRENE IS BEING STEERED AROUND A NEARBY DEEP LAYER RIDGE CENTERED OVER BERMUDA. DATA FROM LAST NIGHT'S SYNOPTIC SURVEILLANCE MISSION DOES NOT SEEM TO HAVE LED TO ANY SIGNIFICANT CHANGES TO EITHER THE INITIAL CONDITIONS OR THE FORECASTS FROM THE VARIOUS DYNAMICAL MODELS. THE MODELS REMAIN IN GENERAL AGREEMENT THAT IRENE WILL ROUND THE RIDGE AND TURN TOWARD THE NORTH DURING THE NEXT 36 HOURS AND NORTHEASTWARD BEYOND 72 HOURS. NONE OF THE MODELS INDICATE LANDFALL ON THE EAST COAST OF THE UNITED STATES. DUE TO THE INITIAL MOTION ADJUSTMENT AND TO A SLIGHT EASTWARD TREND IN THE MODEL TRACKS... THE OFFICIAL FORECAST IS ADJUSTED TO THE RIGHT OR EAST OF THE PREVIOUS ADVISORY DURING THE FIRST THREE DAYS. IT IS ALSO FASTER SINCE IRENE IS GAINING LATITUDE MORE QUICKLY NOW AND WILL BECOME EMBEDDED IN THE WESTERLIES TO THE NORTH OF THE RIDGE AND BEGIN ACCELERATING ON DAY 4... AS SHOWN BY ALL OF THE MODELS EXCEPT THE LEFT-OUTLYING GFDN. SINCE IRENE IS STILL ON THE CUSP OF BECOMING A HURRICANE... IT COULD DO SO AT ANY TIME. THE SHIPS PEAKS AT 63 KT IN 72 HOURS... WHILE THE GFDL PEAKS NEAR 80 KT AROUND THAT SAME TIME. THE OFFICIAL INTENSITY FORECAST IS ADJUSTED ONLY SLIGHTLY DOWNWARD COMPARED TO THE PREVIOUS ADVISORY... TO COME MORE IN LINE WITH SHIPS. SINCE THE NEW OFFICIAL FORECAST IS FASTER... IRENE IS EXPECTED TO REACH COOLER WATERS SOONER... SO A WEAKENING TREND IS INTRODUCED AT THE END OF THE FORECAST... IN ACCORDANCE WITH BOTH GFDL AND SHIPS. FORECASTER KNABB FORECAST POSITIONS AND MAX WINDS INITIAL 13/0900Z 30.1N 68.6W 60 KT 12HR VT 13/1800Z 31.0N 69.3W 65 KT 24HR VT 14/0600Z 32.6N 69.8W 65 KT 36HR VT 14/1800Z 34.2N 69.8W 70 KT 48HR VT 15/0600Z 36.0N 69.2W 70 KT 72HR VT 16/0600Z 38.0N 66.5W 75 KT 96HR VT 17/0600Z 39.5N 62.0W 70 KT 120HR VT 18/0600Z 41.5N 54.0W 60 KT |
