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| #381590 (Received by flhurricane at: 10:43 AM 07.Oct.2010) TCDAT2 TROPICAL STORM OTTO DISCUSSION NUMBER 6 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172010 1100 AM AST THU OCT 07 2010 OTTO HAS FINALLY TRANSITIONED INTO A TROPICAL CYCLONE BASED ON A 07/0935Z AMSU VERTICAL TEMPERATURE ANALYSIS PROFILE FROM UW-CIMSS THAT INDICATED THE WARM CORE HAD MOVED UPWARD FROM THE MID-LEVELS TO THE UPPER-LEVELS OF THE CYCLONE. A RECENT BURST OF DEEP CONVECTION WITH CLOUD TOP TEMPERATURES NEAR -80C THAT HAS DEVELOPED OVER THE CENTER ALSO SUPPORTS A TRANSITION TO TROPICAL CYCLONE STATUS. SATELLITE INTENSITY ESTIMATES ARE RUNNING BETWEEN T2.0/30 KT AND T2.5/35 KT FROM TAFB...SAB...AND UW-CIMSS USING A CURVED BAND PATTERN. HOWEVER...USING A SHEAR PATTERN WITH THE RECENT BURST OF CENTRAL CONVECTION YIELDS A VALUE OF T3.5/55 KT. SINCE THE CONVECTION HAS ONLY PERSISTED FOR ABOUT 3-4 HOURS...THE INITIAL INTENSITY WILL BE MAINTAINED AT 50 KT FOR THIS ADVISORY...BUT THE 50-KT WIND RADII DISTANCE HAS BEEN REDUCED FROM 45 NMI TO 15 NMI. OTTO HAS ESSENTIALLY BEEN STATIONARY FOR THE PAST 6 HOURS...BUT A SLOW DRIFT TO THE NORTHEAST...OR 325/02...IS EXPECTED TO BEGIN SOON AND THAT IS THE MOTION USED FOR THIS ADVISORY. OTHERWISE...THERE REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACKS OR PHILOSOPHIES FOR THE PAST 24 HOURS. A LARGE DEEP-LAYER TROUGH ALONG THE U.S. EAST COAST IS EXPECTED TO CONTINUE ITS EASTWARD TREK AND GRADUALLY NUDGE OTTO TO THE NORTHEAST DURING THE NEXT 24 HOURS. BY 36-48 HOURS...HOWEVER...THE LARGE TROUGH IS FORECAST TO CAPTURE OTTO AND ACCELERATE IT TO THE NORTHEAST AHEAD OF A STRONG COLD FRONT. OTTO IS EXPECTED TO MERGE WITH THE FRONTAL SYSTEM BY 72 HOURS AND BECOME A SIGNIFICANT EXTRATROPICAL CYCLONE THAT COULD AFFECT THE AZORES ISLANDS IN 96 TO 120 HOURS. THE OFFICIAL FORECAST TRACK IS BASICALLY JUST AN UPDATE OF THE PREVIOUS TRACK AND IS CLOSE TO THE CONSENSUS MODEL...TVCN. NOW THAT OTTO HAS TRANSITIONED INTO A TROPICAL CYCLONE...THE STORM HAS A BETTER CHANCE OF REACHING HURRICANE STATUS AS FORECAST BY THE GFDL AND HWRF MODELS. THE VERTICAL SHEAR IS EXPECTED TO REMAIN AROUND 10 KT OR LESS FOR THE NEXT 24 HOURS WHILE OTTO WILL BE OVER 28C OR WARMER SSTS. THE MUCH SMALLER INNER CORE WIND FIELD ALSO SHOULD ALLOW FOR A MORE RAPID RESPONSE TO DEEP CONVECTION THAT DEVELOPS NEAR THE CENTER. IN THE LATER FORECAST PERIODS...THE INTENSITY HAS BEEN HELD A LITTLE HIGHER THAN WHAT WOULD TYPICALLY BE EXPECTED FOR A CYCLONE EXPERIENCING SHEAR CONDITIONS OF 40-50 KT DUE TO EXTRATROPICAL TRANSITION AND AN EXPECTED INFUSION OF BAROCLINIC ENERGY THAT SHOULD HELP TO SUSTAIN THE CIRCULATION. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND IS A BLEND OF THE NHC OBJECTIVE INTENSITY GUIDANCE. FORECAST POSITIONS AND MAX WINDS INITIAL 07/1500Z 23.8N 68.0W 50 KT 12HR VT 08/0000Z 24.3N 67.1W 55 KT 24HR VT 08/1200Z 25.7N 65.0W 60 KT 36HR VT 09/0000Z 27.6N 61.8W 65 KT 48HR VT 09/1200Z 29.8N 57.2W 60 KT 72HR VT 10/1200Z 34.7N 45.2W 55 KT...POST-TROP/EXTRATROP 96HR VT 11/1200Z 39.0N 32.5W 45 KT...POST-TROP/EXTRATROP 120HR VT 12/1200Z 39.0N 25.0W 35 KT...POST-TROP/EXTRATROP $$ FORECASTER STEWART |
