An area of broad low pressure formed in the western Caribbean Sea on September 22nd. Showers and thunderstorms consolidated around the cyclone, and became organized enough for the system to be considered a tropical storm on the 24th and a hurricane on the 25th while moving through the Yucatan Channel into the Gulf of Mexico. Helene intensified as it accelerated offshore western Florida, lured north by an upper level low dropping into the Mid-South. The interaction with this upper level feature helped Helene grow in size and acted as a positive interaction towards lowering its pressure and maintaining a much lower pressure after the storm moved inland. It also linked Helene's rainfall pattern with a front situated around its northern side, which prolonged heavy rainfall across the western Carolinas and portions of Georgia and the Florida Panhandle. Helene became a major hurricane to the west of Tampa on the afternoon of the 26th and moved ashore the Florida Big Bend, west-southwest of Perry, that night. Pressures in southern Georgia near its path were measured as low as 946.8 hPa, which is the lowest known pressure recorded in the state from any cyclone, tropical or otherwise (previous lowest was during Michael, 947.5 hPa at Donalsonville). A broad area of September low pressure records were set with Helene across the Southeast and Ohio Valley.Helene continued northward, becoming a tropical storm in east-central Georgia early on the 27th. The track curled back to the north and then north-northwest during its extratropical transition, occluding in the early afternoon. Helene then coupled with the upper level low that was steering it while turning west across Kentucky, then dropped southeast and east-southeast on the 28th into early on the 29th before its circulation center became ill-defined.
The graphics below show the storm total rainfall for Helene, which used rain gage information from National Weather Service River Forecast Centers, xMACIS2, National Weather Service Forecast Offices, and CoCoRAHS.
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