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| #291558 (Received by flhurricane at: 4:43 AM 27.Aug.2009) TCDAT5 TROPICAL STORM DANNY DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL052009 500 AM EDT THU AUG 27 2009 DATA FROM NOAA BUOY 41047 AND THE AIR FORCE RECONNAISSANCE AIRCRAFT HAVE BEEN CRITICAL IN LOCATING THE BROAD AND ELONGATED CIRCULATION OF DANNY THIS MORNING...WHICH APPEARS TO HAVE MADE ANOTHER NORTHWARD REFORMATION. THE AIR FORCE PLANE FOUND 55 KT WINDS AT 850 MB AND DROPSONDE AND RELIABLE SFMR WINDS OF ABOUT 45 KT. AN EARLIER NOAA HURRICANE HUNTER AIRCRAFT SHOWED 12000 FT WINDS OF 66 KT AND RELIABLE SFMR VALUES OF 45-50 KT. THE NOAA SFMR DATA ALSO REASONABLY FIT A 2254 UTC QUIKSCAT PASS WHICH HAD A FEW 50 KT WIND BARBS. THEREFORE...THE ADVISORY INTENSITY IS SET TO 50 KT. IT SHOULD BE NOTED THAT DANNY DOES NOT HAVE A TYPICAL TROPICAL CYCLONE STRUCTURE AND HAS MOST OF THE STRONG WINDS LOCATED WELL NORTH AND EAST OF THE CENTER. WITH ALL THE CENTER REFORMATIONS...THE INITIAL MOTION IS JUST ABOUT IMPOSSIBLE TO DETERMINE...BUT THE BEST ESTIMATE IS 315/9. DESPITE THE INITIAL UNCERTAINTY...THE MODELS ARE IN EXCELLENT AGREEMENT ON A TURN TOWARD THE NORTH ON FRIDAY AS DANNY MOVES BETWEEN A RIDGE OVER THE WESTERN ATLANTIC OCEAN AND A SHORTWAVE TROUGH OVER THE SOUTHEASTERN UNITED STATES. THE STORM SHOULD THEN ACCELERATE NORTHEASTWARD DUE TO INCREASING FLOW AHEAD OF A LARGER TROUGH OVER THE GREAT LAKES. THE OFFICIAL FORECAST IS SHIFTED EASTWARD BECAUSE OF THE CENTER REFORMATION AND THE GOOD TRACK MODEL AGREEMENT. HOWEVER...ANY SIGNIFICANT DEVIATION TO THE WEST OF THE FORECAST TRACK WOULD BRING DANNY CLOSER TO THE U.S. EAST COAST. WHILE SHEAR IS RELATIVELY LIGHT NEAR DANNY FOR THE TIME BEING... GLOBAL MODELS INCREASE THE SHEAR WITHIN A DAY OR SO. DESPITE THIS PATTERN CHANGE...ALL OF THE RELIABLE INTENSITY MODELS MAKE DANNY A HURRICANE IN A COUPLE OF DAYS...AND MOST OF THE GLOBAL MODELS SHOW THE SYSTEM INTENSIFYING DESPITE THE SHEAR. SOME OF THIS INCREASE IN STRENGTH COULD BE DUE TO BAROCLINIC INFLUENCES AS THE GLOBAL MODELS ARE SHOWING A RATHER DIFFLUENT PATTERN NEAR THE TROPICAL CYCLONE WITH STRONG JET DYNAMICS. HOWEVER...THIS WOULD ARGUE MORE FOR A STRONG EXTRATROPICAL CYCLONE RATHER THAN A TROPICAL CYCLONE. THE OFFICIAL FORECAST STILL SHOWS THIS SYSTEM TO BE A HURRICANE IN A COUPLE OF DAYS BUT GIVEN THE SEEMINGLY UNFAVORABLE ENVIRONMENT... THE NHC FORECAST IS LOWER THAN MOST OF THE GUIDANCE AND MAKES DANNY EXTRATROPICAL BY 72 HOURS. FORECAST POSITIONS AND MAX WINDS INITIAL 27/0900Z 27.4N 72.1W 50 KT 12HR VT 27/1800Z 28.4N 73.1W 50 KT 24HR VT 28/0600Z 30.0N 74.0W 55 KT 36HR VT 28/1800Z 32.3N 74.0W 60 KT 48HR VT 29/0600Z 35.7N 72.9W 65 KT 72HR VT 30/0600Z 44.0N 66.5W 65 KT...EXTRATROPICAL 96HR VT 31/0600Z 50.0N 55.0W 50 KT...EXTRATROPICAL 120HR VT 01/0600Z 53.0N 40.0W 35 KT...EXTRATROPICAL $$ FORECASTER BLAKE |
