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#211586 (Received by flhurricane at: 11:03 PM 29.Aug.2008) TCDAT3 TROPICAL STORM HANNA DISCUSSION NUMBER 8 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL082008 1100 PM EDT FRI AUG 29 2008 CONVENTIONAL SATELLITE IMAGERY SUGGESTS THAT HANNA REMAINS WITHIN A VERY HARSH VERTICAL WIND SHEAR ENVIRONMENT. THE SURFACE CIRCULATION...EXPOSED WELL WEST OF THE REMAINING CONVECTIVE BAND...PASSED ABOUT 60 MILES NORTH OF BUOY 41043 WHICH RECORDED A SEA LEVEL PRESSURE OF 1004 MB. CONSEQUENTLY...HANNA'S CENTRAL PRESSURE IS INCREASED SLIGHTLY TO 1002 MB BASED ON THIS DATA. A QUIKSCAT OVERPASS JUST CAME IN A FEW MINUTES AGO AND INDICATED THAT THE CIRCULATION MAY BE JUST A BIT SOUTH OF THE ADVISORY POSITION AS WELL AS ALSO REVEALING A FEW BELIEVABLE 40-45 KT WINDS OVER THE NORTHEAST QUADRANT. THEREFORE...THE INITIAL INTENSITY IS HELD AT 45 KT. THE GLOBAL MODELS CONTINUE TO INDICATE THAT THE UPPER-LEVEL LOW LOCATED A FEW HUNDRED MILES WEST-NORTHWEST OF CYCLONE WILL EITHER INCREASE IN DISTANCE BETWEEN THE TWO FEATURES WITH TIME OR WEAKEN AND OPEN UP INTO A TROUGH. THE SHIPS MODEL FOLLOWS SUIT BY SUGGESTING THAT THE SHEAR WILL DECREASE IN 12 TO 24 HOURS...WHICH IS REFLECTED IN THE INTENSITY FORECAST WITH GRADUAL STRENGTHENING THROUGH THE 72 HOUR PERIOD. THROUGH THE REMAINING PORTION OF THE FORECAST...THE LARGE-SCALE MODELS SHOW STRONG NORTH TO NORTHWESTERLY UPPER-LEVEL WINDS SETTING UP OVER THE WESTERN ATLANTIC...WHICH COULD ALSO BE INFLUENCED BY HURRICANE GUSTAV'S OUTFLOW PATTERN. SINCE THERE IS A CONSENSUS IN THE DEVELOPMENT OF AN INHIBITING SYNOPTIC UPPER-LEVEL PATTERN...A WEAKENING IS INDICATED THROUGH DAY 5. INITIAL MOTION IS ESTIMATED AT 295/12...WITHIN THE DEEP LAYER EAST-SOUTHEASTERLY FLOW OF THE SUBTROPICAL RIDGE TO THE NORTH OF THE CYCLONE. THE FORECAST PHILOSOPHY REMAINS INTACT FROM THE PREVIOUS ADVISORY...WHICH FOLLOWS CLOSELY TO THE DYNAMICAL MODEL BLEND THROUGH 72 HOURS. BEYOND THE DAY 3 PERIOD...THE OFFICIAL FORECAST IS NUDGED TOWARD THE PREVIOUS TRACK AND A BLEND OF THE GFS AND UKMET MODELS WHICH APPEAR TO BE DEPICTING THE SHEARED VERTICAL STRUCTURE OF THE SYSTEM MORE ACCURATELY. FORECAST POSITIONS AND MAX WINDS INITIAL 30/0300Z 22.1N 65.3W 45 KT 12HR VT 30/1200Z 22.9N 67.0W 50 KT 24HR VT 31/0000Z 23.9N 69.2W 55 KT 36HR VT 31/1200Z 24.5N 70.8W 60 KT 48HR VT 01/0000Z 24.6N 72.1W 65 KT 72HR VT 02/0000Z 24.4N 73.4W 65 KT 96HR VT 03/0000Z 23.6N 75.0W 60 KT 120HR VT 04/0000Z 23.0N 76.3W 55 KT $$ FORECASTER ROBERTS |