Hurricane Ian underwent an eyewall change, turning a disheveled mess into a monster

Hurricane Ian was a collision of every ingredient needed to build a leviathan storm of record magnitude.

But there was one variable — a capricious event in the raucous center of the cyclone — that compounded the rage.

Late Tuesday, Ian underwent what meteorologists call an eyewall replacement cycle, in which the spiraling storm center contracts under intense pressure until it can no longer take the burden and collapses.

In some cases, the still-mysterious phenomenon can disrupt a storm, allowing dry air to push its way into the very heart of the cyclone, causing it to weaken or dissolve entirely.

In Ian’s case, it strengthened it.

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The eyewall expanded, extending the reach of the fiercest winds at its core to a devastating reach of 35 miles. Furious thunderstorms lined up symmetrically like a Slinky, adding more punch. And the overall size ballooned, enough to fit 2004's Hurricane Charley comfortably within its scope. That allowed Ian to push an unprecedented amount of water into Southwest Florida’s frayed coastline.

Ruination followed.

“I’m not sure how many truly grasp what just happened tonight with Hurricane Ian,” meteorologist Michael Lowry wrote on Twitter at 11:41 p.m. Tuesday. “Ian went through a full eyewall replacement cycle, hardly blinked, grew by 50% and delivered the 3rd highest storm surge since 1913 to Key West in the process. Just wow.”

The National Hurricane Center bumped up its forecast for storm surge following the replacement cycle and a rapid intensification that shot Ian from a 120-mph Category 3 hurricane at 4 a.m. Wednesday to a near-Category 5 with 155-mph winds just three hours later.

Ian went from "disheveled mess" to "worst case scenario" at landfall

A peak surge forecast of 16 feet for areas that included Fort Myers Beach, Sanibel Island, Charlotte Harbor, Englewood and Bonita Beach was raised to 18 feet. Areas south of Bonita Beach to Chokoloskee were hiked one foot to a maximum of 12. South of Chokoloskee to East Cape Sable went from 7 feet to 8 feet.

The hurricane center had warned for days that surge would be the killer in Ian. Three different color-coded graphics depicted how deep and how far inland surge would travel. If the threat of a rushing 16-foot wall of water hadn't scared people enough to evacuate — which is done based on storm surge heights, not wind — it was probably too late when it jumped to 18 feet.

"The most important thing to talk about today is the storm surge," said interim National Hurricane Center Director Jamie Rhome in a Tuesday online forecast. "We are trying to communicate to you that it can be that bad."

Rhome spearheaded the program that developed storm surge maps that carefully calculate the angle of storms and the bathymetry of the coastline to better warn of what is possible. Groundbreaking inundation maps were debuted in 2016.

Still, it's hard to fathom what a combination of near-Category 5 winds and a relentless battering of water can do.

“Ian went through the complete cycle offshore and by the time it reached land it was the worst-case scenario,” said Phil Klotzbach, a hurricane researcher with Colorado State University. “You had a very large storm with strong winds and a slow forward motion that added insult to injury.”

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The National Hurricane Center in its second forecast for Tropical Depression Nine on Sept. 23 specifically said the bubbling spin of thunderstorms 930 miles southeast of Havana would rapidly intensify. Rapid intensification is when a storm's wind speeds grow by 35 mph in 24 hours or less.

But the would-be Ian struggled for days. Klotzbach called it a “disheveled mess” and at one point thought the storm would be a “complete bust.”

It gained momentum when harassing wind shear abated and it found the equivalent of the fountain of youth for tropical cyclones — a deeply warm pocket of water around the Gulf of Batabano on Cuba’s southwest coast.

Waiting for Ian on the southwest coast was also a supercharged battery pack of heated water in the pristine Gulf of Mexico untouched by a tropical cyclone this season. A storm ahead of Ian could have churned up cooler water and created a potential speed bump.

“What is so illuminating is the fact that there are incredibly warm sea-surface temperatures right along the path that Ian took,” said Jeff Weber, an atmospheric scientist at the National Center for Atmospheric Research. “We’re talking near 90 degrees and very warm to depth.”

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As Ian channeled the surface heat of the ocean into energy, there was just more energy beneath it.

“When it came off of Cuba and got that perfect eyewall and it looked like Katrina, I knew it would be a classic Category 4 or 5 storm,” Weber said.

Ian had a buffet of warm water leading it to Florida, no biting wind shear to tear it apart, steering winds tugged at it every so lightly, nudging it along at slow 9 to 10 mph and helping vent it like a flue in a chimney, adding to its power.

An average hurricane moves at about 12 to 14 mph, said meteorologist Jeff Masters, co-founder of Weather Underground and a writer for Yale Climate Connections.

Ian and Charley far different storms that defy comparisons

Masters said because Ian and Charley made landfall on Cayo Costa north of Captiva, people compared the two storms. They were worlds apart.

Ten hours before landfall, Ian’s area of hurricane-force winds was 2.9 times larger than Charley. Jonathan Erdman, a meteorologist with The Weather Company, said Charley’s tropical storm-force wind field was about 125 nautical miles, whereas Ian’s was 290.

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Charley was also a fast mover, hitting the state at 20 to 25 mph. That gave it little time to build up much in the way of storm surge.

And there was one other difference, Charley didn’t undergo an eyewall replacement cycle.

“It was getting ready to near the time of landfall, but it didn't happen,” Masters said.

Masters said he was hoping Ian might mimic 2016’s Hurricane Matthew, which underwent an eyewall replacement cycle when it was a Category 4 colossus forecast to buzzsaw up Florida’s east coast. The cycle allowed dry air into the storm and may have helped wobble it away from the coast.

Matthew made landfall in South Carolina as a Category 1 hurricane.

“Matthew never recovered from its eyewall replacement cycle. Ian was able to recover and come ashore as a high-end Cat 4,” Masters said.

Storm surge comes down to a mathematical equation

One way to measure how high storm surge will be is an equation using the integrated kinetic energy of a storm’s surface winds and how big of an area they are blowing over. Charley rated a 7 on an index that ranks kinetic energy. Ian had an index of 47.

Superstorm Sandy ranked 141. Wilma came in at 103.

Masters also noted in his Climate Connections column with meteorologist Bob Henson that sea levels on the southwest coast of Florida are about a foot higher than they were 100 years ago because of human-caused climate change. Higher sea levels increase storm surge damage.

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“The damage is shocking but not surprising,” Masters said about the devastation Ian wrought. “Climate change will affect hurricanes in ways that will surprise us, sometimes for the worse, and sometimes for the better.”

Some research shows that a warmer Earth may mean fewer hurricanes because there could be more shredding wind shear killing budding storms before they can form, but the storms that do form may be more intense.

This article originally appeared on Palm Beach Post: Hurricane Ian's eye changed, worsening storm surge and destructive winds