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| #42673 (Received by flhurricane at: 10:44 PM 28.Aug.2005) TCDAT3 TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER 2 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 11 PM EDT SUN AUG 28 2005 TROPICAL DEPRESSION THIRTEEN CONTINUES TO STRUGGLE WITHIN THE MODERATE NORTHEASTERLY SHEAR ENVIRONMENT. SHORTWAVE INFRARED IMAGERY DEPICTS A RATHER DISORGANIZED CLOUD PATTERN...WITH DEEP CONVECTION DISPLACED TO THE SOUTHWEST OF THE CIRCULATION CENTER. SATELLITE CLASSIFICATIONS AND THE INITIAL INTENSITY REMAIN UNCHANGED FROM THE PREVIOUS PACKAGE. THE INTENSITY FORECAST IS A LITTLE PROBLEMATIC. AVAILABLE DYNAMICAL MODELS SUGGEST DISSIPATION WITHIN 48 HOURS AS THE SYSTEM INTERACTS WITH A MID-ATLANTIC TROUGH TO THE NORTHWEST. SHIPS SUGGESTS THAT THE SHEAR WILL DECREASE BY MID PERIOD...GRADUALLY BRINGING THE SYSTEM TO 61 KT IN 120 HOURS. THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND THE GFDL...INDICATING SLOW STRENGTHENING TO A TROPICAL STORM IN 48 HOURS. INITIAL MOTION IS ESTIMATED AT 310/10. THE TROPICAL DEPRESSION IS EXPECTED TO MOVE WITHIN THE STEERING FLOW AROUND THE SOUTHWESTERN EDGE OF THE SUBTROPICAL RIDGE. GLOBAL MODELS AND THE GFDL SUGGEST A RELATIVELY SHARP TURN TO THE NORTH IN 48 HOURS NEAR 54W JUST BEFORE DISSIPATION. ANOTHER POSSIBLE SCENARIO IS THAT THE SYSTEM COMPLETELY SHEARS FROM THE MID-LEVEL CIRCULATION AND CONTINUES ON A WEST-NORTHWESTWARD MOTION WITH THE LOW-LEVEL FLOW. THE OFFICIAL FORECAST IS A BLEND OF THE GFS BETA ADVECTION MODELS...THE GFDL...AND THE PREVIOUS FORECAST CALLING FOR A GRADUAL TURN NORTHWESTWARD WITHIN A WEAKNESS IN THE RIDGE IN 72 HOURS. FORECASTER ROBERTS/FRANKLIN FORECAST POSITIONS AND MAX WINDS INITIAL 29/0300Z 15.9N 47.4W 25 KT 12HR VT 29/1200Z 16.9N 48.7W 25 KT 24HR VT 30/0000Z 18.1N 50.7W 30 KT 36HR VT 30/1200Z 19.2N 52.8W 30 KT 48HR VT 31/0000Z 20.4N 54.8W 35 KT 72HR VT 01/0000Z 22.5N 58.0W 35 KT 96HR VT 02/0000Z 24.0N 60.0W 35 KT 120HR VT 03/0000Z 25.5N 62.0W 35 KT |
