As the final hours approached before Hurricane Idalia hit Florida, it had grown into a Category 4 storm, lurking ominously off the state’s west coast. The forecast suggested it would keep getting stronger until it hit land. At 6 a.m. on Wednesday, the National Hurricane Center gave a sobering update, reporting that an Air Force Reserve Hurricane Hunter aircraft had recorded winds up to 130 mph (215 kph).
But, as the sun began to rise an hour later, there was a surprising development. The hurricane seemed to be undergoing an “eyewall replacement,” a process where the storm essentially replaces the wall around its eye. This phenomenon, experts say, can temporarily weaken the hurricane. By 7 a.m., the maximum winds had dropped to around 125 mph (205 kph).
Then came another twist in the story. The hurricane made a last-minute turn that spared the state’s capital city, Tallahassee, from more serious damage. Meteorologist Kelly Godsey, who was tracking the storm at the National Weather Service in Tallahassee, explained that eyewall replacement cycles are common in major hurricanes. When this happens, the eyewall essentially collapses, which, in this case, worked in Tallahassee’s favor. According to Donald Jones, a National Weather Service meteorologist, a new eyewall typically forms several hours after this process begins, and the hurricane can intensify. However, there wasn’t enough time for this to happen before Idalia made landfall.
Meteorologist Ryan Maue compared the process to a figure skater pulling in her arms to spin faster. After a successful eyewall replacement cycle, the hurricane ends up with a larger eye and a broader wind field, which can extend the potential damage over a larger area. However, in Idalia’s case, it tracked over land, and the friction from the land surface immediately reduced the wind speeds near the surface.
Ultimately, the hurricane changed its course and made landfall near Keaton Beach, Florida, rather than hitting Tallahassee. This last-minute turn saved Tallahassee from more devastating impacts. Had the storm not changed course, the consequences could have been much worse.
Despite the effects of the eyewall replacement cycle, Idalia remained a major hurricane, posing a threat of storm surges of up to 15 feet (4.6 meters) along some parts of Florida’s coast. According to Kelly Godsey, the energy that drives the storm surge had already been transferred to the water surface, so the surge was already on its way.
During an eyewall replacement cycle, the hurricane can also see an expansion of its wind field, which means a larger area could experience hurricane-force winds. However, this process doesn’t significantly affect the thunderstorms or tornadoes generated by the hurricane, as those typically occur in the outer bands of the storm, far from the eye.
In Tampa, as forecasters tracked the storm’s progress up the coast toward the Big Bend region, the mood was tense. Meteorologist Christianne Pearce at the National Weather Service office in Tampa described the elevated stress levels but emphasized the importance of their work in making decisions to help save lives.
After making landfall, Idalia moved quickly, with a forward speed of around 18 mph (30 kph), according to the National Hurricane Center. While this prevented the storm from dumping excessive amounts of rain on the region, it also allowed it to maintain its intensity as it moved across south Georgia.
One of the notable aspects of Idalia was the exceptionally high water levels recorded in Charleston, South Carolina, and other areas along the Southeast coast. This was a combination of factors, including a “supermoon” high tide, storm-surge effects from Idalia, and long-term sea level rise associated with climate change caused by human activities.
Allison Michaelis, an assistant professor at Northern Illinois University, found several aspects of Idalia intriguing. She noted the contrast between the drought of major hurricanes making landfall from 2006 to 2016 and the six major hurricanes that made landfall across the Gulf Coast since the 2017 season. The location of Idalia’s landfall in the Big Bend Coast of Florida was also uncommon for hurricanes. This serves as a reminder that regardless of how quiet or active previous hurricane seasons have been, it only takes one storm to make a significant impact.