235 WTNT42 KNHC 030252 TCDAT2 Potential Tropical Cyclone Seven Discussion Number 2 NWS National Hurricane Center Miami FL AL072018 1100 PM EDT Sun Sep 02 2018 There has been little change in the organization of the disturbance since the previous advisory. Satellite imagery shows that some new convective bands have formed to the northeast of the trough axis, but there is still no evidence of a closed surface circulation at this time. The initial intensity remains 25 kt, which is in agreement with the earlier ASCAT data and recent surface observations. An Air Force Reserve Unit reconnaissance aircraft is scheduled to investigate the disturbance on Monday to give a better assessment of the structure and intensity of the system. The disturbance will be moving over warm waters and within an area of generally low vertical wind shear. These conditions should allow gradual development of the system over the next day or so. The global model guidance indicates that the surface trough will sharpen and that a closed surface circulation is likely to develop in association with the system over the Gulf of Mexico within the next 24-36 hours. Once this occurs, the system is expected to continue to gradually strengthen until it reaches the north-central Gulf coast Tuesday night or early Wednesday. The intensity guidance did not change much this cycle and neither has the latest official forecast. The initial motion estimate is 300/13 kt. The disturbance is forecast to move west-northwestward to northwestward around the southwestern portion of a deep-layer ridge that is centered over the Mid-Atlantic states. On this heading, the disturbance is expected to pass over the Florida Keys or the southern Florida peninsula tomorrow morning, then cross the eastern Gulf of Mexico Monday night before approaching the north-central Gulf coast late Tuesday or Tuesday night. The dynamical model guidance is in good agreement on this scenario, however, since the system is still in the pre-genesis phase future changes regarding the exact track and timing of the onset of hazards are possible. Key Messages: 1. Potential Tropical Cyclone Seven will bring heavy rainfall and gusty winds to portions of the Bahamas, South Florida, and the Florida Keys tonight and Monday, and interests in those areas should monitor the progress of this system. 2. A Tropical Storm Watch has been issued for portions of the central Gulf Coast, and tropical storm conditions are possible in those areas Tuesday night and Wednesday. Heavy rainfall from this system will affect portions of the central Gulf Coast later this week, including areas that are currently receiving heavy rainfall from a different weather system. Interests in these areas should monitor products from their local National Weather Service office. 3. Users should be aware that forecast uncertainty for potential tropical cyclones is generally larger than that for tropical cyclones, especially beyond 48-72 hours. FORECAST POSITIONS AND MAX WINDS INIT 03/0300Z 23.4N 78.7W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 03/1200Z 24.5N 80.7W 30 KT 35 MPH 24H 04/0000Z 25.9N 83.4W 35 KT 40 MPH 36H 04/1200Z 27.5N 86.2W 40 KT 45 MPH 48H 05/0000Z 28.8N 88.6W 50 KT 60 MPH 72H 06/0000Z 31.7N 92.5W 30 KT 35 MPH...INLAND 96H 07/0000Z 33.2N 94.4W 25 KT 30 MPH...INLAND 120H 08/0000Z 34.2N 95.7W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Brown