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| #372243 (Received by flhurricane at: 4:50 PM 29.Aug.2010) TCDAT1 HURRICANE DANIELLE DISCUSSION NUMBER 34 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL062010 500 PM AST SUN AUG 29 2010 DEEP CONVECTION AROUND DANIELLE HAS BECOME RATHER ASYMMETRIC WITH MOST OF THE COOL CLOUD TOPS OCCURRING IN THE CYCLONE'S NORTHERN SEMICIRCLE. CORRESPONDING...DVORAK CURRENT INTENSITY ESTIMATES FROM SAB AND TAFB ARE DROPPING WITH 3.5...OR 55 KT...AND 4.0...OR 65 KT...RESPECTIVELY. FORTUNATELY...A FORTUITOUS ASCAT PASS WAS RECEIVED FROM 1404Z WHICH SHOWED SEVERAL BELIEVABLE HURRICANE FORCE WIND VECTORS. A CIMSS AMSU INTENSITY ESTIMATE FROM A 1626Z NOAA-19 OVERPASS EVEN SUGGESTED CATEGORY TWO INTENSITY...THOUGH THIS APPEARS TO BE TOO HIGH. THE INITIAL INTENSITY IS SET AT 70 KT AS A BLEND OF THESE. DANIELLE CONTINUES TO EXHIBIT SOME BAROCLINICITY... WHICH IS BEING MANIFEST THROUGH THE COLD AIR ADVECTION ON THE NORTH AND WEST SIDE OF THE CYCLONE. HOWEVER...AS THE SYSTEM MOVES NORTHEASTWARD AND A SURFACE HIGH REMAINS NEARLY STATIONARY OVER THE MID-ATLANTIC STATES...THE EXTRATROPICAL TRANSITION SHOULD BE DELAYED. DANIELLE CONTINUES TO ACCELERATE TOWARD THE NORTH-NORTHEAST WITH A CURRENT SPEED OF ABOUT 25 KT. THERE WAS CONCERN THAT WE WERE FOLLOWING A MID-LEVEL VORTEX RATHER THAN THE SURFACE CIRCULATION. HOWEVER...GEOSTATIONARY VISIBLE AND POLAR ORBITING MICROWAVE IMAGERY SUGGESTS THAT THE VORTEX IS STILL COHERENT VERTICALLY. DANIELLE SHOULD DECELERATE SOME AND TURN TOWARD THE EAST-NORTHEAST BY TOMORROW UNDER THE INFLUENCE OF A VIGOROUS SHORTWAVE TROUGH TO ITS NORTHWEST AND A SUBTROPICAL RIDGE TO ITS SOUTHEAST. MOST OF THE MODELS LOSE THE VORTEX IN ABOUT 48 HR WHEN THE SYSTEM BECOMES EXTRATROPICAL. THIS IS BECAUSE THERE IS A PROMINENT BAROCLINIC DEVELOPMENT JUST NORTH OF DANIELLE...WHICH MAY RESULT IN THE VORTEX FROM DANIELLE BECOMING ABSORBED AT THAT TIME. ASSUMING THAT DANIELLE REMAINS THE PRIMARY CYCLONE AFTER EXTRATROPICAL TRANSITION...A TRACK FORECAST IS PROVIDED THROUGH 96 HR. THE FORECAST TRACK IS FASTER THAN THE PREVIOUS ADVISORY AND MODEL CONSENSUS FOR THE NEXT 24 HR BECAUSE OF THE FASTER INITIAL MOTION THAN ANTCIPATED...AND THEN SIMILAR TO BOTH THEREAFTER. UNTIL EXTRATROPICAL TRANSITION IN ABOUT TWO DAYS...DANIELLE SHOULD WEAKEN GRADUALLY DUE TO MODERATE VERTICAL SHEAR AND DECREASING SSTS UNDER ITS TRACK. THE OCEAN PREDICTION CENTER PROVIDED POSITION... INTENSITY...AND SIZE GUIDANCE FOR THE EXTRATROPICAL PORTION OF DANIELLE. THE 1404Z ASCAT PASS ALLOWED FOR A SLIGHT ENLARGEMENT OF THE 34...50...AND 64 KT WIND RADII ESTIMATED FOR THE INITIAL TIME. FORECAST POSITIONS AND MAX WINDS INITIAL 29/2100Z 38.0N 54.5W 70 KT 12HR VT 30/0600Z 40.1N 52.9W 65 KT 24HR VT 30/1800Z 41.3N 50.2W 60 KT 36HR VT 31/0600Z 42.3N 45.5W 55 KT 48HR VT 31/1800Z 44.0N 39.0W 60 KT...POST-TROP/EXTRATROP 72HR VT 01/1800Z 51.0N 30.0W 60 KT...POST-TROP/EXTRATROP 96HR VT 02/1800Z 57.6N 32.5W 50 KT...POST-TROP/EXTRATROP 120HR VT 03/1800Z...DISSIPATED $$ FORECASTER LANDSEA/BERG |
