A large area of low pressure developed just east of central American around September 22. The sprawling system drifted generally northward, but the counterclockwise flow brought extreme rains especially to the Pacific coasts of Nicaragua, Honduras, and El Salvador. The next day, the disturbance began to organize over the eastern Caribbean, but lacked a defined center. On the 24th, it became organized enough to be named Tropical Storm Helene.
When Helene formed, its center was exposed to the west of the main convective mass due to some shear out of the southwest. However, this shear was already diminishing; high oceanic heat content and atmospheric humidity soon put the storm on a strengthening trend as it moved northwestward. Helene was a large storm, with gale force radii above the 90th percentile of historical Atlantic cyclones at the same latitude. As a result, the core was slow to consolidate, but impacts were very widespread. When the storm passed just west of the northeast tip of the Yucatan Peninsula during the morning of September 25, tropical storm force winds already extended more than 250 miles from the center in some directions. Around the same time, Helene strengthened into a hurricane.
The hurricane began to feel the flow ahead of a trough over the central United States later that day and accelerated toward the north, entering the Gulf of Mexico. Overnight, the core of Helene steadily became better defined and an eye began to emerge. Once the eyewall was well-established, the intensification accelerated on September 26. The storm reached category 2 that morning and became a major hurricane that afternoon. By the early evening, Helene's forward speed had increased to more than 20 mph toward the north-northeast and it was closing in quickly on the Gulf coast. It reached category 4 soon after, reaching a peak intensity of 140 mph winds and a central pressure of 938 mb at landfall in the big bend region of Florida late on September 26, local time.
The large size and fast motion of the storm meant that the storm surge impacts to the concave area of coastline were very severe. On top of that, hurricane-force winds spread far inland and into Georgia before the storm could spin down significantly. The wind damage was severe for a large swath of the southeast, especially just east of the center's path. Helene weakened to a tropical storm over central Georgia and only lost tropical storm status over Tennessee during the afternoon of the 27th; the cyclone became post-tropical that evening. Its remnants slowed to a standstill near the Tennessee valley and slowly diminished, but the combination of Helene-influenced rains before the arrival of the storm and ex-Helene stalling over the area led to some of the storm's heaviest rainfall amounts in the region, especially western North Carolina. What was left of the hurricane finally dissipated by early on September 29.
The image above is a nighttime infrared satellite view of Hurricane Helene at peak intensity as a category 4 hurricane just before its landfall in Florida. The storm's uncommonly large windfield caused widespread damage.
Helene was a relatively short-lived but large and devastating storm.
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