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| #25569 (Received by flhurricane at: 4:52 AM 10.Jun.2005) TCDAT1 TROPICAL STORM ARLENE DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT FRI JUN 10 2005 ARLENE HAS A RAGGED APPEARANCE IN SATELLITE IMAGERY THIS MORNING... WITH MOST OF THE ASSOCIATED CONVECTION IN A POORLY-DEFINED BAND NORTHEAST OF THE EXPOSED LOW-LEVEL CENTER. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND A BROAD AND POORLY-DEFINED WIND CENTER...A 1000 MB CENTRAL PRESSURE...AND FLIGHT-LEVEL WINDS OF 56 KT AT 850 MB NEAR THE ISLE OF YOUTH. HOW MUCH OF THIS WIND IS REACHING THE SURFACE IS QUESTIONABLE...AS THE CONVECTION IN THE AREA IS SOMEWHAT ISOLATED AND THE ISLE OF YOUTH REPORTED 20 KT WINDS AT 06Z. HOWEVER...THESE FLIGHT-LEVEL ARE STRONG ENOUGH TO JUSTIFY INCREASING THE INITIAL INTENSITY TO 40 KT. ARLENE HAS TURNED TO THE LEFT OVER THE PAST 6 HR AND THE INITIAL MOTION IS NOW 340/7. WATER VAPOR IMAGERY SHOWS A LARGE MID/UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO...WITH A BUILDING RIDGE OVER THE WESTERN ATLANTIC AND THE EASTERN UNITED STATES. THIS COMBINATION SHOULD STEER ARLENE GENERALLY NORTH-NORTHWESTWARD UNTIL IT REACHES THE NORTHERN GULF COAST IN 36-48 HR. DYNAMICAL MODELS GENERALLY AGREE WITH THIS SCENARIO...WITH SOME SPREAD IN BOTH THE TRACK AND SPEED. THE OFFICIAL FORECAST IS DOWN THE MIDDLE OF THE GUIDANCE ENVELOPE...CALLING FOR ACCELERATION TOWARD THE NORTH-NORTHWEST DURING THE NEXT 24 HR FOLLOWED BY SOME SLOWING AS ARLENE APPROACHES THE COAST. THE NEW TRACK IS IN BEST AGREEMENT WITH THE UKMET AND IS SHIFTED A LITTLE TO THE LEFT OF THE PREVIOUS FORECAST. THE INTENSITY FORECAST REMAINS PROBLEMATIC. ON THE STRENGTHENING SIDE...LARGE-SCALE MODELS SUGGEST THE VERTICAL SHEAR SHOULD DECREASE SOMEWHAT DURING THE NEXT 24 HR AS ARLENE MOVES OVER THE FAIRLY WARM WATERS OF THE LOOP CURRENT. ON THE OTHER HAND...THE BROAD WIND STRUCTURE AND LARGE AMOUNTS OF DRY AIR SEEN IN WATER VAPOR IMAGERY NEAR ARLENE BOTH ARGUE AGAINST STRENGTHENING. THE SHIPS MODEL CALLS FOR THE STORM TO REACH 45-50 KT INTENSITY BEFORE LANDFALL... WHILE THE GFDL CALLS FOR A 64 KT INTENSITY AT LANDFALL. THE INTENSITY FORECAST WILL COMPROMISE BETWEEN THE TWO MODELS... CALLING FOR ARLENE TO REACH 55 KT BEFORE LANDFALL. THE FORECAST TRACK AND WIND RADII REQUIRE A TROPICAL STORM WATCH FOR THE NORTHERN GULF COAST AT THIS TIME. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 10/0900Z 21.6N 84.8W 40 KT 12HR VT 10/1800Z 23.4N 85.7W 40 KT 24HR VT 11/0600Z 26.2N 87.2W 45 KT 36HR VT 11/1800Z 28.5N 88.3W 50 KT 48HR VT 12/0600Z 31.0N 88.8W 55 KT 72HR VT 13/0600Z 37.0N 87.0W 30 KT...INLAND 96HR VT 14/0600Z 42.0N 82.0W 25 KT...INLAND DISSIPATING 120HR VT 15/0600Z...DISSIPATED |
