The National Hurricane Center (NHC) has initiated advisories on Potential Tropical Cyclone One (PTC 1), located near the northeastern tip of the Yucatan Peninsula. PTC 1 is expected to become a tropical storm on Friday and make landfall over the southwestern Florida peninsula on Saturday afternoon. After that, PTC 1 is expected to accelerate northeastward with some slight additional intensification possible. Tropical Storm Watches have already been issued for western Cuba, the southern Florida peninsula, and the northwestern Bahamas. The 1991-2020 average date for the first Atlantic named storm is June 20, so if PTC 1 develops into a tropical storm, it will be well ahead of climatology despite the Atlantic pre-season tropical development streak ending.

As of 7:00 p.m. CDT (8:00 p.m. CDT), Potential Tropical Cyclone One was centered near 21.5°N 87.5°W, and was moving northward at about 5 mph. Maximum sustained winds were 30 knots (35 mph), with an estimated minimum pressure of 1003 mb. The NHC currently gives PTC 1 a 90 percent chance of development, both within 48 hours and five days. If PTC 1 becomes a tropical storm, it will be named Alex. PTC 1 does not appear to have a well-defined low-level circulation yet, but a broad low pressure area is centered near the northeastern tip of the Yucatan Peninsula. An Air Force Hurricane Hunter aircraft investigated PTC 1 this afternoon, and was unable to fix a defined center of circulation. Within the next 12 hours or so, PTC 1’s circulation is likely to become better defined, which would result in its designation as a tropical cyclone. An Air Force Hurricane Hunter aircraft is scheduled to investigate PTC 1 again tomorrow morning and will investigate if a better defined low-level circulation has developed. PTC 1 should move slowly northward tonight, before speeding up a bit and turning northeastward tomorrow. A Tropical Storm Watch is currently in effect for the following areas: the west coast of Florida south of the Middle of Longboat Key, the east coast of Florida south of the Volusia/Brevard County Line, the Florida Keys including the Dry Tortugas, Lake Okeechobee, Florida Bay, the Cuban provinces of Matanzas, Mayabeque, Havana, Artemisa, Pinar del Rio, and the Isle of Youth, and the Northwestern Bahamas. A Tropical Storm Watch means that tropical storm conditions (sustained winds of at least 39 mph and heavy rainfall) are possible within the next 48 hours.

Based on the 18:00 UTC Thursday SHIPS guidance, vertical wind shear is expected to be greater than 20 knots (25 mph) for the next 5 days, at times being greater than 30 knots (35 mph). This should limit intensification, despite sufficiently warm sea surface temperatures. The strong southwesterly shear should result in PTC 1 being a disheveled system, with the heaviest rainfall south and east of the center. A possible interaction with an upper-level trough could allow some intensification after PTC 1’s circulation passes over Florida, though it is unclear if the cyclone will be fully tropical in nature at that time. Since PTC 1 is expected to be well offshore, impacts along the United States east coast will likely be limited to heavy surf and not rainfall or strong winds. The latest NHC forecast currently expects PTC 1 to remain tropical throughout the entire 120 hour period, however.