What is rapid intensification in hurricanes, and is it happening more often?

Nicole Mortillaro · CBC News

· Posted: Jul 05, 2024 4:00 AM EDT | Last Updated: 14 minutes ago

Hurricanes are the most powerful forces of nature on our planet. They can produce winds upwards of 275 km/h or stronger, along with intense rainfall and storm surges. And these effects can be felt for hundreds of kilometres from the centre of the storm. 

Climate scientists believe that, as we continue to pump more and more greenhouse gases into the atmosphere, which warms the planet including our oceans — hurricanes are changing.

Some of the effects of climate change include hurricanes producing more rainfall, moving further inland in the Atlantic, and — more concerning to many climate scientists — rapid intensification.

Last week, Beryl went from a Category 1 to a Category 4 in just 24 hours, eventually jumping to a Category 5. It was the earliest Category 4 and 5 on record for the Atlantic basin. 

Along with two other rapidly strengthening storms last season, that's three instances of rapid intensification in just five hurricane months (the season runs from June 1 to November 30).

"Based on the data that we have, over the last few decades, it used to be a really rare situation that a hurricane or a tropical storm would increase in intensity over 24 hours by such a large amount," said Gabriel A. Vecchi, professor of geosciences at Princeton University in New Jersey.

"It's becoming a more and more common event."

What is rapid intensification?

The U.S. National Hurricane Center (NHC) defines rapid intensification as "an increase in the maximum sustained winds of a tropical cyclone of at least 30 kt [56 km/h] in a 24-hour period."

However, some climate scientists say that there is no hard and fast rule. 

Just like how a hurricane doesn't suddenly jump in danger if it passes the threshold between Category 4 and 5, there isn't one useful measure of  "rapid," said Andra Garner, assistant professor in the department of environmental science at Rowan University, in Glassboro, New Jersey.

"So you know, I think there is nuance there. And, you know, you always kind of need to keep that in mind that just because it doesn't specifically fit the definition, that doesn't mean it's not still a dangerous storm." 

Hurricanes form from atmospheric disturbances and warm, tropical water. You can think of warm water as the fuel for hurricanes.

"When we get up in the morning, we have our cup of coffee to kind of get us going. That caffeine is really important for a lot of us," Garner said. "For our hurricane, you've got those warm ocean waters that are kind of like the caffeine, and when we're kind of warming the planet and when we're making those ocean waters much warmer than they usually are. It's like an extra shot of caffeine in the coffee." 

And with ocean temperatures increasing — and reaching record highs in 2023 and into 2024 — it's like giving hurricanes a shot of espresso.

Is this happening more often?

In 2023, rapid intensification joined the likes of polar vortex and atmospheric rivers as new weather terms in public vernacular. 

First there was Hurricane Idalia in August that jumped from a Category 1 to a Category 4 in just 24 hours. It eventually hit the area of Big Bend, Fla., as a Category 3, causing widespread damage. 

Then, two months later, Hurricane Otis stunned climate scientists. 

Initially, when the tropical depression formed on Oct. 21 in the Pacific Ocean, forecasters had only called for it to develop into a tropical storm. Even in the subsequent days, the NHC had only forecast that Otis would be near hurricane strength at landfall and that heavy rainfall would be the main threat.