‘Rapid intensification’ often happens as hurricanes near shore – what does that mean?

(NEXSTAR) – It usually takes several days to even a week for a tropical storm to grow into a powerful hurricane. But if conditions are just right, a major hurricane can develop in just hours.

Some may remember this happening with Hurricane Laura in 2020. The process, known as “rapid intensification,” took Laura from a tropical storm with sustained winds of 65 mph to a Category 3 with 115 mph winds in a matter of hours.

Helene strengthened into a Category 2 hurricane Thursday, and forecasters warned that the storm would continue to intensify as it crosses the Gulf of Mexico on a path to Florida. It’s possible that the storm could undergo rapid intensification before hitting land Thursday evening.

A storm like this undergoes rapid intensification when its maximum sustained winds increase at least 35 mph in 24 hours or less, according to the National Hurricane Center. That’s a jump of about two categories on the Saffir-Simpson scale, which grades hurricane strength from 1 to 5.

Hurricane Michael, in 2018, was another major hurricane in the Gulf of Mexico to rapidly intensify. It increased 46 mph in 24 hours as it approached landfall in the Florida Panhandle.

Both hurricanes Katrina and Rita, during the historic 2005 season, rapidly intensified before releasing devastating damage to the Gulf Coast.

Even if Helene does not meet the definition of a rapidly intensifying storm, it is expected to bring damaging winds, rains and flash floods hundreds of miles inland across much of the southeastern U.S.

The governors of Florida, Georgia, the Carolinas and Virginia have all declared emergencies in their states.

The Associated Press contributed to this report.

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