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| #291730 (Received by flhurricane at: 10:34 PM 27.Aug.2009) TCDAT5 TROPICAL STORM DANNY DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052009 1100 PM EDT THU AUG 27 2009 DANNY REMAINS VERY DISORGANIZED IN ITS SATELLITE PRESENTATION. LITTLE DEEP CONVECTION HAS BEEN NOTED NEAR THE ESTIMATED CENTER. THERE ARE A FEW CLUSTERS OF DEEP CONVECTION OVER THE EASTERN AND NORTHERN PORTIONS OF THE CIRCULATION...BUT THIS CONVECTION SHOWS LITTLE OR NO EVIDENCE OF BANDING FEATURES. DROPSONDE DATA FROM THE NOAA G-IV JET AIRCRAFT SUGGEST THAT THE CYCLONIC CIRCULATION OF DANNY HAS LITTLE VERTICAL DEPTH. A NOAA P-3 HURRICANE HUNTER AIRCRAFT...CONDUCTING A RESEARCH MISSION IN DANNY THIS EVENING... INDICATES THAT THE STRONGEST WINDS CONTINUE TO BE DISPLACED WELL TO THE NORTHEAST OF THE CENTER. PEAK WINDS REPORTED BY THE PLANE WERE 42 KT...SO THE INITIAL INTENSITY IS REDUCED TO 40 KT FOR THIS ADVISORY. DANNY HAS BEEN EXPERIENCING STRONG WEST-SOUTHWESTERLY SHEAR DUE TO AN UPPER-LEVEL TROUGH AND CYCLONIC SHEAR AXIS TO ITS WEST. THERE IS STILL A WINDOW OF OPPORTUNITY FOR THE STORM TO STRENGTHEN AS GLOBAL MODELS SHOW THE UPPER-LEVEL FLOW BECOMING MORE ANTICYCLONIC...WITH SOME LESSENING OF THE SHEAR DURING THE NEXT 24 HOURS. THEREFORE THE OFFICIAL FORECAST SHOWS SOME STRENGTHENING OVER THE NEXT DAY OR SO. HOWEVER BY 48 HOURS THE SHEAR OVER DANNY IS EXPECTED TO BE 40 KT OR MORE SO ANY INTENSIFICATION OF THE SYSTEM AS A TROPICAL CYCLONE SHOULD CEASE BY THAT TIME. IN FACT...BY 48 HOURS...THE GLOBAL MODELS AND THE FSU CYCLONE PHASE SPACE ANALYSES IMPLY THAT DANNY MAY HAVE ALREADY BECOME AN EXTRATROPICAL CYCLONE. THE CENTER MEANDERED ABOUT DURING THE DAY...BUT LAST-LIGHT VISIBLE IMAGERY AND DATA FROM THE AIRCRAFT INDICATED THAT A NORTH TO NORTH-NORTHWESTWARD MOTION BEGAN SEVERAL HOURS AGO. HOWEVER...THE CENTER IS NEARLY IMPOSSIBLE TO DISCERN ON RECENT INFRARED IMAGES. THE INITIAL MOTION IS AN UNCERTAIN 330/7. THE TRACK FORECAST REASONING IS BASICALLY UNCHANGED. DANNY SHOULD MOVE ON A GENERALLY NORTHWARD COURSE DURING THE NEXT DAY OR SO ON THE EAST SIDE OF A SHORT WAVE TROUGH OVER THE SOUTHEASTERN UNITED STATES. THEREAFTER A DEEPENING LONG WAVE TROUGH OVER THE EASTERN U.S. SHOULD CARRY DANNY OR ITS POST-TROPICAL COUNTERPART NORTH-NORTHEASTWARD TO NORTHEASTWARD AT AN INCREASED FORWARD SPEED. LATE IN THE FORECAST PERIOD...THE CYCLONE SHOULD TURN EASTWARD AS IT BECOMES WELL EMBEDDED IN THE MID-LATITUDE WESTERLIES. THE OFFICIAL FORECAST IS VERY SIMILAR TO THE PREVIOUS ONE AND IS CLOSE TO THE MODEL CONSENSUS. SINCE THE FORECAST TRACK CONTINUES TO KEEP THE AREA OF TROPICAL STORM FORCE WINDS OFFSHORE...NO ADDITIONAL WATCHES OR WARNINGS ARE BEING ISSUED FOR THE U.S. EAST COAST AT THIS TIME. HOWEVER NEW WATCHES AND/OR WARNINGS COULD BE REQUIRED ON FRIDAY...PARTICULARLY IF THE FORECAST TRACK SHIFTS TO THE WEST. FORECAST POSITIONS AND MAX WINDS INITIAL 28/0300Z 28.4N 73.5W 40 KT 12HR VT 28/1200Z 29.7N 74.5W 45 KT 24HR VT 29/0000Z 32.5N 74.5W 50 KT 36HR VT 29/1200Z 36.5N 73.0W 55 KT 48HR VT 30/0000Z 40.5N 69.5W 55 KT 72HR VT 31/0000Z 47.5N 59.0W 50 KT...EXTRATROPICAL 96HR VT 01/0000Z 50.5N 46.0W 40 KT...EXTRATROPICAL 120HR VT 02/0000Z 51.0N 31.5W 35 KT...EXTRATROPICAL $$ FORECASTER PASCH/BERG |
