How Hurricane Isaias got so dangerously strong so fast
Scientific American · LC · trust 47/100
The Category 3 storm intensified overnight—and is headed toward the U.S. Gulf Coast. Here’s what to know
Hurricane Isaias as it approached the U.S. Gulf Coast as a Category 3 hurricane on October 9, 2026.
Just one day ago Hurricane Isaias was a Category 1 hurricane. Overnight, it ballooned into a major Category 3 storm with 120-mile-per-hour winds and is set to slam into the U.S. Gulf Coast Friday evening with “life-threatening storm surge,” “devastating winds” and the potential for tornadoes, according to the U.S. National Oceanic and Atmospheric Administration (NOAA).
So how did this storm get so dangerous so quickly?
For one, Isaias’s presence alone is something of an anomaly. As Scientific American previously reported , Isaias is the first hurricane to form in the Atlantic region this season, setting a record for the latest first arrival of any hurricane since satellite monitoring began.
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Meteorologists say Isaias’s late formation is largely because of the presence of El Niño, a pattern of unusually warm ocean waters in the eastern Pacific Ocean that can alter weather patterns across the planet. During El Niño years, hurricane activity in the Atlantic typically drops thanks to choppy wind conditions in the atmosphere, or increased vertical wind shear .
But when that wind shear happens to weaken, any burgeoning storm can quickly grow wherever there’s abundant warm ocean water. And there is plenty of that in the Gulf right now.
And the storm may have particularly gotten a boost from a large, deep warm-water eddy in the Gulf of Mexico, hurricane specialist Michael Lowry wrote on Substack. This blob of exceptionally warm water formed by spinning off of the Gulf’s Loop Current that is notorious for boosting hurricane strength. The eddy is giving Isaias a “second wind” as it nears landfall, Lowry wrote.
Warm ocean water fuels tropical cyclones, explains Kim Wood, an associate professor of hydrology and atmospheric sciences at the University of Arizona. “The warmer ocean waters are, the more energy is available, especially if those waters are warm through a deep layer,” Wood says. As a storm’s wind pushes the ocean’s surface water, water deeper down swells up to replace it, they add. If that water is warm—as it would be in this eddy—it can serve as “a longer-lasting energy source” for the storm.
A hurricane warning—meaning hurricane conditions are expected—is in effect for parts of Mississippi, Alabama and Florida, with wind, rain and flooding risks expected throughout the wider Gulf Coast region, including in Louisiana and Georgia, and well inland, NOAA predicts. Isaias isn’t expected to weaken until after it makes landfall.
Gulf Coasters in Isaias’s path should look out for local guidance on how to prepare for the storm’s arrival, including any potential evacuation orders, according to NOAA.
Jackie Flynn Mogensen is a breaking news reporter at Scientific American . Before joining SciAm, she was a science reporter at Mother Jones, where she received a National Academies Eric and Wendy Schmidt Award for Excellence in Science Communications in 2024. Mogensen holds a master’s degree in environmental communication and a bachelor’s degree in earth sciences from Stanford University. She is based in New York City.
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