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#371936 (Received by flhurricane at: 10:59 AM 28.Aug.2010) TCDAT1 HURRICANE DANIELLE DISCUSSION NUMBER 29 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062010 1100 AM AST SAT AUG 28 2010 THE VISIBLE AND INFRARED SATELLITE PRESENTATIONS AND A SERIES OF MICROWAVE IMAGES FROM THE NRL TROPICAL CYCLONE WEBSITE INDICATE CONTINUED WEAKENING OF THE INNER EYEWALL STRUCTURE OF DANIELLE...PARTICULARLY OVER THE WESTERN PORTION. THE OUTER CONCENTRIC RING LOCATED ABOUT 60 NMI FROM THE CENTER OF THE CYCLONE...HOWEVER...IS WELL DEFINED AND SYMMETRIC...AND APPEARS TO BE CLOSE TO COMPLETING AN EYEWALL REPLACEMENT CYCLE. CONSEQUENTLY...THERE MAY BE A SMALL WINDOW OF OPPORTUNITY FOR STRENGTHENING DURING THE NEXT 12-18 HOURS BEFORE THE NORTHEASTERLY SHEAR INCREASES SIGNIFICANTLY AND THE SYSTEM BEGINS ITS TRACK OVER COOLER WATER. IT IS WORTH NOTING...HOWEVER...THAT THE SHIPS MODEL PROBABILITY OF RAPID INTENSIFICATION DURING THE NEXT 24 HOURS HAS DECREASED FROM 14 TO 4 PERCENT...SUGGESTING A SMALL CHANCE OF THIS SCENARIO COMING TO FRUITION. AS A COMPROMISE...THE INITIAL AND FORECAST INTENSITY WILL MAINTAIN A WIND SPEED OF 95 KT FOR 12 HOURS...THEN SHOW A GRADUAL WEAKENING TREND THEREAFTER. BY THE 96 HOUR PERIOD...DANIELLE WILL LIKELY TRANSITION INTO A LARGE AND POWERFUL EXTRATROPICAL CYCLONE OVER THE NORTH ATLANTIC...AND THE FORECAST SHOWS ONLY SLOW WEAKENING DURING THIS EVENT. THE INITIAL MOTION ESTIMATE IS NORTH-NORTHEASTWARD OR 020/8. DANIELLE SHOULD BEGIN TO ACCELERATE TOWARD THE NORTH-NORTHEAST LATER TODAY IN RESPONSE TO A DEEP LAYER BAROCLINIC TROUGH MOVING OFF OF THE EASTERN SEABOARD OF THE UNITED STATES. A TEMPORARY REDUCTION IN FORWARD SPEED IS FORECAST NEAR THE 36-48 PERIOD AS A MID-LEVEL RIDGE PASSES TO THE NORTH OF THE CYCLONE. AT DAY 3...ANOTHER MAJOR SHORTWAVE TROUGH IS EXPECTED TO MOVE OUT OF NORTHEAST CANADA...CAUSING DANIELLE TO AGAIN ACCELERATE EAST-NORTHEASTWARD. THE AFOREMENTIONED SHORTWAVE TROUGH SHOULD CAUSE DANIELLE TO SHARPLY TURN NORTHWARD TOWARD THE END OF THE PERIOD. THE OFFICIAL NHC FORECAST HAS BEEN ADJUSTED A LITTLE TO THE RIGHT BECAUSE OF THE 6 HOUR MOTION AND IS BASED ON A BLEND OF THE DYNAMICAL MODELS...PRIMARILY THE GFS...ECMWF...AND THE CANADIAN BEYOND DAY 3. FORECAST POSITIONS AND MAX WINDS INITIAL 28/1500Z 29.3N 60.5W 95 KT 12HR VT 29/0000Z 31.2N 59.5W 95 KT 24HR VT 29/1200Z 34.6N 57.2W 90 KT 36HR VT 30/0000Z 37.7N 54.9W 85 KT 48HR VT 30/1200Z 39.5N 53.0W 75 KT 72HR VT 31/1200Z 42.5N 42.5W 70 KT 96HR VT 01/1200Z 51.0N 30.5W 65 KT...POST-TROP/EXTRATROP 120HR VT 02/1200Z 55.0N 35.5W 55 KT...POST-TROP/EXTRATROP $$ FORECASTER ROBERTS/AVILA |