TALLAHASSEE, FLORIDA: Meteorologists often discuss sudden changes in a storm’s strength caused by something called an ‘eyewall replacement cycle.’ These cycles are a common occurrence with powerful hurricanes and typhoons and can temporarily weaken their impact.
The eyewall replacement cycle is a phenomenon where a new eye begins to form around the old one. Eventually, the old eye is replaced by the new one, which gradually reduces in size.
Just before Hurricane Idalia was about to hit Florida’s west coast as a Category 4 monster, it took an unexpected turn – an eyewall replacement cycle – ultimately sparing Tallahassee, the state’s capital, from more significant damage, as reported by the Daily Mail.
During an eyewall replacement cycle, a hurricane’s intensity typically decreases. For instance, a Category 5 hurricane might drop to Category 4 due to the gradual weakening of the inner eyewall.
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However, as the outer eyewall organizes and contracts, the storm’s intensity can rebound. But it’s uncommon for a hurricane to maintain Category 5 status for an extended period because of these cycles.
While an eyewall replacement cycle can lower a hurricane’s category, it also spreads hurricane-force winds over a larger area, making more regions vulnerable to severe destruction.
Kelly Godsey, a meteorologist at the National Weather Service in Tallahassee, explained, “Eyewall replacement cycles are common in major hurricanes, and when you see that, it does lead to some temporary weakening.”
The frequency of extreme hurricanes has risen dramatically in recent years, offering more opportunities to observe these cycles. However, predicting when an eyewall replacement cycle will happen remains a significant challenge for forecast models.
How long does an eyewall replacement cycle last? According to NOAA, it can range from 12 to 18 hours and may take 2 to 3 days to complete. These cycles can occur multiple times during a tropical cyclone’s course.
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For instance, Typhoon Mawar, which made landfall in Guam in late May, underwent an eyewall replacement cycle just before hitting the coast, reducing some of the storm’s power.
The eyewall of a tropical storm is its most deadly and destructive part. The winds are the strongest, the rainfall is the heaviest, and dense convective clouds can reach heights of 49,000 feet.
Rapid changes in atmospheric pressure near the eye generate significant pressure gradient forces that drive the powerful winds. At around 1,000 feet above the surface, the winds reach their highest speeds.
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In the case of Hurricane Idalia, it was initially classified as a Category 4 hurricane but was downgraded to Category 3 due to the eyewall replacement cycle. This natural process is potentially life-saving as it weakens the hurricane just before landfall.
Thanks to the eyewall replacement cycle, Hurricane Idalia had a larger eye and an expanded wind field, increasing the potential for damage across a wider area. However, it chose to veer over land, where surface friction immediately slowed its winds.
As the eyewall replacement process continued, the hurricane made an abrupt turn away from Tallahassee, home to around 200,000 people, Florida State University, and thousands more in the surrounding area. Instead, it made landfall near Keaton Beach.
Godsey, who, along with his colleagues, stayed inside the meteorological office to monitor the situation, stated, “Had that turn not occurred, there would have been much more devastating impacts here in Tallahassee.”
Despite the effects of the eyewall replacement cycle, Idalia remained a potent hurricane, posing a threat of storm surges up to 15 feet along parts of Florida’s coast.
According to Yale Climate Connections meteorologist and journalist Bob Henson, Idalia’s inland path over the Southeast United States was relatively straightforward for a storm traveling near the coast.