How can hurricane Ian go from hurricane, to tropical storm, and now back to hurricane?
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When it goes back over water, which it is doing now that it’s off the Atlantic coast of Florida, that can fuel an increase in intensity.
Hurricanes gain power when they move over warm water and lose power when they cross over land or cold oceans.
Ian grew rapidly when it passed into the Gulf of Mexico and started sucking up all that bathwater-warm energy.
Then it passed over land and spent all that energy tossing boats through peoples front doors in Ft Myers.
Eventually it cleared Florida entirely and wandered out over the Atlantic again, where it can start sucking up energy from warm oceans again.
Generally speaking, while over water the storm increases in strength and while over land it decreases in strength. So it hit Florida as a hurricane, passed over Florida, losing strength and becoming a tropical storm, then reached the Atlantic and started to gain strength again, becoming a Hurricane. Based on current trajectory, it’ll hit South Carolina as a hurricane on Friday, then quickly downgrade back to a tropical storm, and further into a tropical depression as it moves into North Carolina and Virginia.
Same way your car can run out of gas, stop running, go to a gas station, now your car can run again
So first we need to know what the difference between a hurricane and a tropical storm is. Hurricanes and tropical storms are both tropical cyclones, meaning that they have a cyclone shape and a distinct “eye,” they look more or less like [this](https://discover.alesolutions.com/wp-content/uploads/2020/05/hurricane-cyclone-typhoon-header.jpg). The difference is how fast the wind is. Wind speeds for these storms is measure in what is called “maximum sustained surface wind,” this measures the wind speed 10 meters above the ground in the eye wall of the storm, the area right before the eye, over a period of 1 minute. A tropical storm has maximum sustained surface winds from 39-73 mph (63-118 km/h), while a hurricane has maximum sustained surface winds of 74 mph (119 km/h) or above. Hurricanes range from a Category 1, with wind speeds from 74-95 mph (119-153 km/h) all the way up to a Category 5, which has wind speeds above 157 mph (252 km/h). A Category 3 or higher, meaning winds above 111 mph (178 km/h) is a “major hurricane.”
Hurricanes gain power when they move over warm water, they basically “feed” on it. Hurricanes lose power when they move over cold water and land. The Gulf of Mexico and the Atlantic Ocean near it are very warm, in July and August the ocean near Key West has an average temperature of 87 degrees Fahrenheit (31 Celsius). This is why Hurricanes can gain strength so rapidly before hitting Florida or the Gulf Coast. So the storm gained strength in the Gulf and became a hurricane, then it hit Florida and weakened as it passed over the land. After it passed over Florida it went back into the Atlantic Ocean and gained more power as it moved over the warm water, becoming a hurricane again.
Hurrricanes/tropical storms/tropical depressions get those names based on how fast the wind is blowing. Out in the water, Ian could go fast and so its speeds were high enough to be called a hurricane. Over land, it slowed down so its speeds were only fast enough to be called a tropical storm. Once it got back over water, it sped up again and met the wind speed requirements to be called a hurricane again.
Hurricane go vroom vroom over warm water. Go putter putter over land. Go vroom over slightly less warm water. Go putter over land.
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