Issued at 1100 AM AST Thu Sep 12 2024
371 WTNT42 KNHC 121449 TCDAT2 Tropical Depression Seven Discussion Number 5 NWS National Hurricane Center Miami FL AL072024 Issued by the NWS Weather Prediction Center College Park MD 1100 AM AST Thu Sep 12 2024 Tropical Depression Seven looks more organized on satellite imagery this morning, with a compact circulation and a small curved band with some deep convection. Subjective and objective Dvorak numbers indicate the system is close to becoming a tropical storm. However, given the relatively small size of ongoing convection near the center, the initial intensity was conservatively held at 30 knots, or at the lower end of the estimates. The cyclone continues on a west-northwestward heading, and the general motion is expected to continue over the next 2-3 days. The forward speed should gradually slow as the subtropical ridge to the north of the system weakens. Track guidance diverges considerably early next week, related to uncertainties with an amplifying trough over the north-central Atlantic Ocean and another ridge centered northeast of the Leeward Islands. This track forecast stays close to the global model consensus and places less weight on the regional hurricane models which depict a considerably weaker and less organized system. This produces a track forecast that is slightly faster and to the left of the previous forecast. While environmental conditions are somewhat favorable for gradual strengthening, with low-moderate vertical wind shear and marginally warm SSTs, intensity guidance came in lower for this cycle. We show the system becoming a tropical storm in the next day, followed by the intensity only slowly increasing to 45 knots in the next five days. However, there is potential for greater strengthening beyond what is shown early next week as the cyclone will be in an environment characterized by lower shear, warmer SSTs around 28C, slightly more instability, but plentiful dry air aloft. The new forecast is a little lower than the previous one, but above the latest model consensus. FORECAST POSITIONS AND MAX WINDS INIT 12/1500Z 17.8N 34.6W 30 KT 35 MPH 12H 13/0000Z 18.5N 36.4W 35 KT 40 MPH 24H 13/1200Z 19.2N 38.6W 35 KT 40 MPH 36H 14/0000Z 19.6N 40.5W 40 KT 45 MPH 48H 14/1200Z 19.7N 42.1W 40 KT 45 MPH 60H 15/0000Z 19.8N 43.6W 40 KT 45 MPH 72H 15/1200Z 20.1N 44.9W 40 KT 45 MPH 96H 16/1200Z 20.6N 46.7W 40 KT 45 MPH 120H 17/1200Z 21.0N 47.8W 45 KT 50 MPH $$ Forecaster Lamers/Bann/Blake
