ATLANTA — Hurricane Helene underwent Rapid Intensification Thursday, climbing from a Category 1 storm to a Category 4 leading up to landfall.
A tropical cyclone "rapidly intensifies" when it has an increase of winds of at least 35 miles per hour in a 24 hour period.
Hurricanes that undergo rapid intensification right before landfall are among the most dangerous storms.
In 2018, Michael intensified from a Category 2 to a Category 5 hurricane the day before it made landfall in the Florida Panhandle. Our 11Alive team was there, covered the widespread damage and devastation from both the winds and also the storm surge.
In 2022, Ian also underwent rapid intensification, leading to a catastrophic storm surge and wind devastation in southwest Florida.
What ingredients make a hurricane rapidly intensify?
First, extremely warm ocean waters. Hurricanes are like steam engines. They use warm, unstable air as fuel. Having extremely warm waters over 85 degrees can be a main factor. That warm bath water doesn't just need to be right at the surface, but also further down in the gulf or ocean waters.
Hurricanes also need a lack of wind shear, which can disrupt a storm's circulation.
Lastly, a storm needs to be in a moisture-rich environment so that thunderstorms can easily wrap all the way around the storm's center. Dry air on any side would limit this and prevent symmetry and a storm's ability to strengthen.
Even though we know these three factors are important, forecasting rapid intensification is still challenging for meteorologists.
Researchers continue to look at past rapidly-intensifying storms with hopes of improving forecast skill and ultimately help decision-makers get the best information to prepare communities.
Some research shows that rapid intensification may become more, not less common, in a warmer atmosphere.
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