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| #1150860 (Received by flhurricane at: 4:44 PM 01.Sep.2023) TCDAT4 Tropical Depression Twelve Discussion Number 2 NWS National Hurricane Center Miami FL AL122023 800 PM CVT Fri Sep 01 2023 A 1458 UTC AMSR-2 microwave pass showed that the depression has a well-defined circulation, however the associated deep convection was rather disjointed. Dvorak CI numbers classifications are still T2.5 from TAFB, but the final-T number dropped to 2.0 from SAB, so the system is still being classified as a 30-kt depression at this time. Some more defined convective bands are now developing within the circulation, so the system may be on its way to becoming a tropical storm. ASCAT data should provide a better handle on the maximum winds of the system this evening. The initial motion is toward the north-northwest (345 degrees) at 10 kt, with the depression situated between a mid-level ridge over western Africa and a mid- to upper-level low over the eastern/central Atlantic. Another ridge near the Azores is expected to force the depression to turn northwest and then west-northwest around the mid-level low during the next few days. The NHC track forecast is a little east of the previous forecast near the multi-model consensus aids, but this is more a function of an adjustment of the initial position. Once the system becomes a remnant low, the low-level flow should turn it toward the northwest and north on days 3 and 4. The depression has a small window of relatively low shear, warm waters, and a sufficiently moist atmosphere to strengthen to a tropical storm tonight or on Saturday, which is shown in the official forecast. However, the system will be moving into a much drier atmosphere with strengthening southerly shear, which should cause weakening to begin in about 36 hours. Organized deep convection could also dissipate in a couple of days, and the cyclone is forecast to become a remnant low by 48 hours. Global model fields suggest the remnant low could last a little bit longer than shown in the previous forecast, and dissipation is now shown a day later on day 5. FORECAST POSITIONS AND MAX WINDS INIT 01/2100Z 20.8N 28.7W 30 KT 35 MPH 12H 02/0600Z 22.2N 29.5W 35 KT 40 MPH 24H 02/1800Z 24.0N 30.8W 35 KT 40 MPH 36H 03/0600Z 25.4N 32.3W 30 KT 35 MPH 48H 03/1800Z 26.3N 33.5W 30 KT 35 MPH...POST-TROP/REMNT LOW 60H 04/0600Z 26.9N 34.6W 25 KT 30 MPH...POST-TROP/REMNT LOW 72H 04/1800Z 27.7N 35.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 96H 05/1800Z 29.4N 35.4W 20 KT 25 MPH...POST-TROP/REMNT LOW 120H 06/1800Z...DISSIPATED $$ Forecaster Berg |
