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#938245 (Received by flhurricane at: 4:51 AM 03.Sep.2018) TCDAT2 Potential Tropical Cyclone Seven Discussion Number 3 NWS National Hurricane Center Miami FL AL072018 500 AM EDT Mon Sep 03 2018 The system is gradually becoming better organized with some increased convective banding features. However, surface and radar data suggest that a well-defined center of circulation has not yet formed. The initial intensity is set at 25 kt in agreement with the latest Dvorak estimates from TAFB and SAB. An Air Force Reserve Unit Hurricane Hunter aircraft is scheduled to investigate the system later this morning, and should provide a better estimate of its intensity and structure. Global model predictions show a closed circulation forming within 12 to 24 hours, so the official forecast calls for tropical cyclone status later today. Although the system should move over the very warm waters of the eastern and north-central Gulf of Mexico during the next 36 hours, the model guidance is not very aggressive about intensification. This may be due to some moderate shear as indicated by the SHIPS model output. The official intensity forecast is similar to the previous one and at the upper end of the numerical guidance suite. The disturbance appears to have picked up some forward speed, and is now moving at around 300/5 kt. A west-northwestward to northwestward motion is likely, along the southwestern periphery of a mid-level anticyclone, until landfall along the northern Gulf coast. The official track forecast is close to the dynamical model consensus and is just slightly to the right of and faster than the previous one. Given the proximity of the 36-hour forecast point to the coast, it is time to change the Tropical Storm Watch to a Warning. 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 today, and interests in those areas should monitor the progress of this system. 2. A Tropical Storm Warning has been issued for portions of the central Gulf Coast, and tropical storm conditions are expected in those areas beginning late Tuesday. Heavy rainfall from this system will affect portions of the central Gulf Coast over the next few days, including areas that have already received 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 03/0900Z 24.5N 80.2W 25 KT 30 MPH...POTENTIAL TROP CYCLONE 12H 03/1800Z 25.7N 82.1W 30 KT 35 MPH 24H 04/0600Z 27.2N 84.8W 35 KT 40 MPH 36H 04/1800Z 28.8N 87.4W 40 KT 45 MPH 48H 05/0600Z 30.4N 89.7W 50 KT 60 MPH 72H 06/0600Z 33.0N 92.7W 30 KT 35 MPH...INLAND 96H 07/0600Z 34.0N 95.0W 25 KT 30 MPH...INLAND 120H 08/0600Z 35.5N 96.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ Forecaster Pasch |