August 31, 2023 Tropical storm Idalia news
Hurricane Idalia caused "significant damage" after it ripped into Florida's Big Bend with 125 mph winds and record-setting storm surge, but the storm's evolution before landfall likely prevented an even worse disaster, Jamie Rhome, deputy director of the National Hurricane Center told CNN.
On Wednesday morning, with the storm just 20 miles and 45 minutes from landfall, the hurricane center announced Idalia's winds dropped 5 mph because it was undergoing an eyewall replacement cycle.
An eyewall replacement cycle is akin to a snake shedding its skin. Strong hurricanes can shed a smaller eyewall — the ring of most intense winds that surrounds the hurricane's calm eye — in favor of a larger one. During this process, the storm's winds can weaken, but when the process is complete, the storm will be larger and can then start to intensify even further.
Idalia's landfall kept this process from completing, preventing the hurricane from being even larger and more intense than forecast at landfall.
"If it would have been six or 12 hours more over water, I think a totally different hurricane would have made landfall," Rhome said.But even an incomplete eyewall cycle could have had a "massive" effect on what people experienced, Rhome said. The hurricane's structure was changing, which affected where the strongest winds were set up and who got the worst surge as a result.
Idalia’s wind field was expanding during the eyewall replacement cycle, which means it may have broadened the scope of the surge at the expense of its peak intensity.
The cycle “would dramatically change where surge happens," Rhome said. "I can't put into words just how sensitive surge is to the wind. Not just the wind speed, but also the wind direction, too. These structural changes can also change the angle of the wind, which can have dramatic impacts on the surge or the timing of the wind (and the surge) relative to the tide."
The tides were another key factor in the severity of the surge, especially in a place like Cedar Key.
"The other thing that happened with Cedar Key is the (storm's) timing changed," Rhome said. "It, luckily, luckily came in at low tide, which probably whacked, you know, four feet off of it (the surge totals), just with that."
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