Timeline of Hurricane Helene (September 24-27, 2024)

• September 20-22: A Central American Gyre (CAG) develops, bringing heavy rains to portions of Nicaragua and Honduras as it moves slowly northward.
• September 23, 1200 UTC: The large circulation of the CAG straddles Central America and the northwestern Caribbean Sea. Deep convection begins to organize near a mid-level vorticity maximum about 130 nautical miles south of Grand Cayman. The system lacks a well-defined low-level center necessary to be a tropical cyclone.
• September 23, 1500 UTC: The National Hurricane Center (NHC) initiates potential tropical cyclone advisories as the system is expected to become a tropical cyclone and bring tropical storm conditions to land areas within the next couple of days.
• September 24: The system becomes Tropical Storm Helene. It enters the Gulf of America as a category 1 hurricane later in the day and turns northward.
• September 25: Tropical storm conditions are observed over portions of the eastern Yucatan Peninsula of Mexico (including Cancun, Cozumel, and Isla Mujeres) and western Cuba. Helene develops a secondary wind maximum farther from the center.
• September 26: Helene rapidly intensifies over the very warm Gulf waters while accelerating north-northeastward. Aircraft reconnaissance reports an eye around 0600 UTC, and a clear eye becomes visible on satellite imagery around 1800 UTC.
• September 26, 1800 UTC: Helene intensifies into a 105-knot major hurricane, located about 150 nautical miles west-southwest of Tampa, Florida.
• September 27, 0000 UTC: Helene reaches its peak intensity of 120 knots, located about 80 nautical miles south-southwest of the coast of the Florida Big Bend region. Its central pressure is estimated to be around 941 mb.
• September 27, 0310 UTC: Hurricane Helene, a category 4 hurricane with winds of 120 knots and a central pressure of 939 mb, makes landfall about 10 nautical miles southwest of Perry, Florida. This is the strongest landfalling hurricane in the Florida Big Bend region since reliable records began around 1900.
• September 27: Helene moves inland, bringing catastrophic storm surge to Florida's Gulf Coast, life-threatening wind gusts far inland across the southeastern United States, and historic rainfall leading to catastrophic flooding and landslides in the southern Appalachians. Numerous tornadoes are produced.
• September 28, 0600 UTC: Helene's sustained winds drop below gale force.
• September 28-29: The remnants of Helene continue to produce impacts, including tropical storm force winds and gusts across portions of the Mid-Atlantic and Ohio Valley as it becomes post-tropical and eventually dissipates.