Issued at 300 PM CST Thu Jun 12 2025
661 WTPZ44 KNHC 122044 TCDEP4 Potential Tropical Cyclone Four-E Discussion Number 1 NWS National Hurricane Center Miami FL EP042025 300 PM CST Thu Jun 12 2025 Showers and thunderstorms associated with an area of low pressure located south of Mexico, that the National Hurricane Center has been monitoring have increased and are showing signs of organization. While some mid-level rotation is evident in visible satellite images near the northeast edge of ongoing convection, the low-level circulation remains broad and elongated. However, the system is expected to become a tropical storm tonight or tomorrow, and it is possible that it will bring tropical storm conditions to land areas within the next 36 to 48 hours. Therefore, the National Hurricane Center is initiating Potential Tropical Cyclone advisories for this disturbance. The initial motion is more uncertain than normal since the system is still in the formative stage, but the best estimate is west-northwestward at about 6 kt. A northwestward to west-northwestward motion is anticipated during the next few days as the system moves parallel to the coast of southwestern Mexico, being steered by a mid-level ridge. Model guidance is in fairly good agreement with the overall track evolution, although minor track shifts may cause greater impacts to the coast of Mexico. The NHC forecast lies near the simple consensus aids. Since the disturbance currently lacks a well-defined center, users are reminded that the track forecast uncertainty is typically larger in these situations, and future track adjustments may be required. The models suggest a more well-defined center should develop overnight or tomorrow. Once the system becomes better organized and develops an inner core, the environmental conditions appear favorable for strengthening during the next couple of days, with warm sea surface temperatures and abundant moisture. However, the system will be dealing with some easterly to northeasterly wind shear. The NHC forecast shows steady strengthening over the next few days, although there are some guidance aids such as HCCA and the hurricane regional models that lie above the current NHC forecast. Given some uncertainty in how quickly the system consolidates and the limiting wind shear, the NHC forecast lies near the simple intensity consensus aids. Beyond day 4, environmental conditions will become hostile which should lead to weakening, and the system should struggle to produce convection moving into cooler SSTs and a more stable air mass. The current NHC forecast has the system becoming a remnant low at that time, and calls for dissipation by day 5. Based on the NHC forecast, Tropical Storm Watches have been issued for portions of southwestern Mexico. KEY MESSAGES: 1. The outer bands of Potential Tropical Cyclone Four-E may bring locally heavy rainfall to the Mexican states of Guerrero, Michoacan, and Colima through this weekend. Isolated flooding and mudslides, especially in areas of steep terrain, are possible. 2. The disturbance is forecast to be at tropical storm strength when it moves near the southwestern coast of Mexico on Saturday. Tropical storm conditions are possible over portions of that area. FORECAST POSITIONS AND MAX WINDS INIT 12/2100Z 11.3N 100.2W 30 KT 35 MPH...POTENTIAL TROP CYCLONE 12H 13/0600Z 12.0N 100.4W 35 KT 40 MPH...TROPICAL CYCLONE 24H 13/1800Z 13.3N 101.3W 45 KT 50 MPH 36H 14/0600Z 14.3N 102.7W 55 KT 65 MPH 48H 14/1800Z 15.5N 104.3W 60 KT 70 MPH 60H 15/0600Z 16.5N 106.2W 60 KT 70 MPH 72H 15/1800Z 17.1N 108.2W 50 KT 60 MPH 96H 16/1800Z 17.3N 112.2W 30 KT 35 MPH...POST-TROPICAL 120H 17/1800Z...DISSIPATED $$ Forecaster Kelly