Here's what you need to know.
- Record-warm oceans counter El Nino -
Back in May, the US National Oceanic and Atmospheric Administration (NOAA) predicted a "near normal" Atlantic hurricane season, which runs from June 1 to November 30.
That was in large part because of the El Nino global weather pattern, which causes a higher than average "vertical wind shear" in the Atlantic, which in turn suppresses hurricane activity.
"If you have big changes in the wind with height, that tends to import dry, lower-energy air into the core of a tropical cyclone and prevent it from strengthening," Allison Wing, an atmospheric scientist at Florida State University, told AFP.
But come August, NOAA increased its forecast prediction for the season to "above normal," based on ocean and atmospheric conditions "such as record-warm Atlantic sea surface temperatures" that "are likely to counterbalance the usually limiting atmospheric conditions associated with the ongoing El Nino event."
"It's been a sort of tricky year in terms of thinking about the whole seasonal forecast because we have these two opposing factors," said Wing.
- What is known about climate change -
One-eye catching example: on July 24 a buoy off the southern tip of Florida recorded an alarming peak temperature of 101.1 degrees Fahrenheit (38.4 Celsius), readings more commonly associated with hot tubs, and a possible new world record.
"Warm waters, both at the surface of the ocean and beneath, provide the fuel that intensifies tropical storms and hurricanes," said Michael Mann, a climatologist at University of Pennsylvania. "That allows them to both intensify faster and attain higher maximum intensities."
You still need the right conditions to lead to hurricane formation -- but when they come along, storms will take advantage of warming oceans to generate fiercer winds and cause bigger storm surges.
"You can think of climate change as sort of like loading the dice," added Wing. "There's still a variety of different possible outcomes for any individual storm, but you have a greater chance of having those high-intensity storms."
Apart from affecting the maximum intensity of hurricanes, climate change can also increase the amount of rain they are able to dump, Andrew Kruczkiewicz, an atmospheric scientist and researcher at the International Research Institute for Climate and Society at Columbia University, told AFP.
"The warmer the atmosphere is, the greater the capacity for water," he said. "This can mean increased intense precipitation events."
Kruczkiewicz added he was personally worried people who had moved inland to escape Idalia could find themselves caught nonetheless in extreme weather.
Last year, climate change boosted Hurricane Ian's rainfall by at least 10 percent, according to recent research.
- Seasons getting longer -
There's increasing evidence that the storm season itself is getting longer, as the window during which ocean surface temperatures support tropical storm formation begins sooner and ends later, said Mann -- a relationship that appears to hold true in both the Atlantic hurricane basin and the Bay of Bengal.
While there is ample research that climate change is making hurricanes more dangerous, whether it is also making them more frequent is much less certain and more study is required.
Storm Idalia lashes Georgia, Carolinas after slamming Florida
Perry, United States (AFP) Aug 31, 2023 -
Florida began assessing the damage Wednesday from Idalia's flooding after the powerful storm inundated coastal communities and knocked out power to thousands, as the system advanced up the southeastern US coast bringing additional rain deluges and dangerous storm surge.
After roaring across the Sunshine State, Idalia barreled into neighboring Georgia and weakened to a tropical storm that nevertheless was drenching the region with up to 10 inches (25 centimeters) of rain and bringing life-threatening storm surges to coastal communities, officials said.
They described Idalia and its record-high surging waters as a once-in-a-lifetime event for the area of northwest Florida most affected.
While there were no immediately confirmed deaths, Florida Governor Ron DeSantis stressed "that very well may change," given the storm's magnitude.
State officials said first responders including search and rescue teams were operational, but warned it could take time to reach more remote areas blocked by fallen trees or high water.
Idalia struck as an "extremely dangerous" Category 3 hurricane in Florida's marshy, sparsely populated Big Bend area around 7:45 am (1145 GMT) Wednesday, the US National Hurricane Center (NHC) reported.
The storm crashed ashore packing maximum sustained winds of approximately 125 miles (215 kilometers) per hour near the community of Keaton Beach, with a possible storm surge of up to 16 feet (about five meters) in some coastal areas, the NHC said.
Though Idalia weakened to a Category 1 hurricane and eventually a tropical storm with winds of 60 miles per hour, it remained dangerous as it raked over Georgia and into South Carolina.
Ben Almquist, emergency management director for Charleston, South Carolina, told CNN late Wednesday: "We still have plenty of floodwaters throughout the city right now," and some rescue operations were underway.
But Thursday morning was shaping up to be Idalia's last gasp.
"Everything should be improving once we pass the (Wednesday) midnight hour for just about everybody," Ron Morales, a meteorologist with the National Weather Service based in Charleston, told the city's The Post and Courier newspaper.
Idalia is forecast to blow out over the Atlantic later Thursday.
- 'Pretty scary' -
Mass evacuations were ordered earlier for thousands of Floridians -- although many defied authorities and hunkered down.
In Perry, a small town in Idalia's path, emergency crews were already cleaning up and residents who stayed behind were assessing the impact.
John Kallschmidt, 76, struggled to push aside a pine tree that fell on the roof of his small wooden house.
"It got pretty scary with all the trees blowing over and coming down," he told AFP. "But it's the way it is, it's life in Florida. You have to get accustomed to this kind of thing."
In coastal Steinhatchee, about 20 miles (32 kilometers) south of Idalia's landfall, streets were mostly deserted hours after the storm inundated virtually the entire town.
Patrick Boland, 73, downplayed the disaster. "It was a little windy," he said. "The trees were coming down in my front yard, but other than that, the house is fine."
- Speedy storm -
In the Tampa Bay area -- a metropolitan zone of some three million people -- streets were submerged and flood waters swept across yards.
Just north in the city of Tarpon Springs, residents waded, or even canoed, to safety as homes and apartments were inundated.
DeSantis told reporters that Idalia moved faster than some of the more disastrous hurricanes that have hit the state in which the eye of the storm idled along the coastline and caused death and severe destruction.
His governor's mansion was not spared damage. A century-old oak tree crashed into a wing of the historic Tallahassee residence. First Lady Casey DeSantis said she was home at the time with their three children, but no one was hurt.
Around 147,000 customers in Florida and 133,000 in Georgia were without electricity early Thursday, according to tracking website PowerOutage.us.
Power was also out for about 34,000 in South Carolina, where the NHC has forecasted flooding.
With the White House calling for storm vigilance, the Federal Emergency Management Agency deployed more than 1,000 emergency personnel to the disaster zone.
"Idalia is the strongest storm... to make landfall in this part of Florida in over 100 years," FEMA Administrator Deanne Criswell said.
The storm dealt a glancing blow to Cuba before moving over the Gulf of Mexico, which scientists say is experiencing a "marine heat wave" -- energizing Idalia's winds as it raced towards Florida.
Record-breaking temperatures off Florida are expected to amplify Atlantic storms this season, with scientists blaming human-caused climate change for the overall warming trend.
"These storms are intensifying so fast that our local emergency management officials have less time to warn and evacuate and get people to safety," Criswell told a press conference on Wednesday.
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