IE 11 is not supported. For an optimal experience visit our site on another browser.

How Hurricane Idalia went from Category 1 to Category 4 overnight

Warmer oceans in recent years have provided the energy for hurricanes to rapidly intensify, a phenomenon that is likely to be more common in a warming climate.
Floodwaters from Hurricane Idalia in Gulfport, Fla, on Aug. 30, 2023.
Floodwaters from Hurricane Idalia in Gulfport, Fla., on Wednesday. Juan Manuel Barrero / Bloomberg via Getty Images

Warm waters in the Gulf of Mexico helped fuel Hurricane Idalia’s rapid intensification hours before it made landfall, a phenomenon that experts say will likely occur more often in a warming world.

As Idalia moved through the Gulf on Tuesday, its winds rose by 55 mph in just 24 hours, strengthening from a Category 1 hurricane to a Category 4 by early Wednesday. It weakened slightly to a Category 3 hurricane before making landfall a few hours later in Florida’s Big Bend, near Keaton Beach.

But Idalia’s intensification as it approached the Florida coast is “to be expected with hotter ocean temperatures,” said Jeff Masters, a former hurricane scientist with the National Oceanic and Atmospheric Administration who now works as a meteorologist for Yale Climate Connections.

The world’s oceans in recent months have shattered temperature records, with multiple bodies of water — including the North Atlantic, the Gulf of Mexico and the Caribbean Basin — engulfed in severe marine heat waves.

Most of the eastern Gulf of Mexico has been 2 to 4 degrees Fahrenheit warmer than average, with isolated spots along the coast, near where Idalia made landfall, up to 5 degrees above average, according to analyses of sea surface temperatures by tropical cyclone forecaster Levi Cowan on his website, Tropical Tidbits.

Masters pointed to a spate of hurricanes since 2017 that have intensified rapidly.

“We’ve seen this movie a lot,” he said. “We saw this with Hurricane Ian last year, though it did weaken a little bit right before landfall. We saw this with Hurricane Ida the year before that in Louisiana. We saw it with Laura. We saw it with Harvey. So a lot of rapid intensifiers right before landfall.”

In a White House briefing Wednesday, FEMA Administrator Deanne Criswell said hurricanes in recent years have intensified rapidly because of elevated ocean temperatures.

These events have added to the challenges faced by local officials in the days and hours before storms hit.

“These storms are intensifying so fast that our local emergency management officials have less time to warn and evacuate and get people to safety,” Criswell said.

There are three main ingredients that can trigger rapid intensification in storms: warm waters, weak upper-level winds and lots of moisture in the atmosphere.

The National Hurricane Center defines “rapid intensification” as an increase in sustained wind speeds of at least 35 mph over 24 hours.

Jill Trepanier, an associate professor and climate scientist at Louisiana State University, said Idalia’s escalation into a Category 4 hurricane was “impressive” and exactly what forecasters were predicting as the storm moved through the warm waters of the eastern Gulf.

Idalia also traveled through a pocket of low wind shear, which describes the change in speed and direction of winds at different atmospheric heights. Strong wind shear can disrupt big storms, causing them to weaken or rip apart entirely.

That’s essentially what happened as Idalia approached the Florida coast, which helped downgrade the storm before it moved on land.

“When a hurricane, which builds from the bottom up, moves into a zone where the upper level winds are really strong, this disrupts its circulation,” said Corene Matyas, a professor in the department of geography at the University of Florida.

Though Idalia weakened into a Category 3 hurricane before making landfall, destruction along the coast is still expected to be severe.

“I’m glad it began weakening quickly for those further inland, but an intensifying event as it is coming toward shore is a more dangerous event,” Trepanier said in an email. “I fear the pictures of what happened.”

Experts have said that rapid intensification could become more common as a result of climate change.

A 2019 paper published in the journal Nature Communications used computer simulations and climate models to study the formation and evolution of tropical cyclones from 1982 to 2009. The researchers found that warmer ocean temperatures from human-caused climate change likely provided the necessary fuel for tropical cyclones to develop and intensify.

Since 2010, several major hurricanes have undergone rapid intensification, including Dorian in 2019, which saw its peak winds increase from 150 mph to 185 mph in the span of only nine hours. Last year, Hurricane Ian underwent two bouts of rapid intensification before it made landfall in southwestern Florida.

Masters noted that Idalia is now one of 10 storms since 1950 that intensified at least 40 mph in the 24 hours before making landfall in the United States.

“Sobering to see five of those storms occurred in the past seven years,” he tweeted Wednesday. “Climate change increases the odds of rapid intensification.”

While scientists know the general conditions that set the stage for rapid intensification, the process itself requires more research. Part of the problem is that there simply isn’t enough data yet to make accurate forecasts of when this phenomenon will occur — and how.

“You need data right near the core of the hurricane over the ocean, and we have a limited observation capabilities there because you can’t fly that low with hurricane cameras. It’s not safe,” Masters said.

Still, researchers know a key ingredient is warmer-than-usual sea surface temperatures.

Masters said that hotter oceans will set the stage for more rapidly intensifying storms in the future.

“We’re continuing to warm the ocean,” he said, “so you ain’t seen nothing yet.”