Intensifying Idalia threatens Florida's Gulf Coast with storm surges

Hurricane Idalia was strengthening on Tuesday as it lumbered toward Florida's Gulf Coast, where officials ordered evacuations and urged millions of residents to brace for a possible major Category 3 storm when it makes landfall on Wednesday.

Idalia was expected to intensify rapidly before slamming ashore on Wednesday morning, according to the Miami-based National Hurricane Center (NHC).

Florida Governor Ron DeSantis urged residents in low-lying areas to heed orders to seek higher ground, warning that the storm surge could cause life-threatening floods.

"If you are told to evacuate, you have to do that now," he said at a Tuesday morning news briefing. Evacuation orders have been issued in 22 counties, and more than 20 emergency shelters have been opened, he said.

The NHC projected Idalia's centre would likely cross Florida's coastline somewhere in the Big Bend region, where the state's northern panhandle curves around into the Gulf side of the Florida Peninsula. The area, roughly between the inland cities of Tallahassee and Gainesville, is much more lightly populated than the Tampa-St Petersburg area to the south.

Despite the latest projection, the path of the intensifying storm was uncertain as it spun northward over the warm waters of the Gulf of Mexico, a day after passing just west of Cuba, where tens of thousands evacuated ahead of flooding and high winds.

Idalia intensified into a hurricane early on Tuesday. It was expected to reach Category 3 force - classified as a major hurricane, with sustained winds of at least 179kph - on the five-step Saffir-Simpson wind scale by the time it reaches Florida on Wednesday, the NHC said.

Surges up to 12 feet high

Most of Florida's 21 million residents, along with many in Georgia and South Carolina, were under hurricane, tropical storm and storm surge warnings and advisories.

By midmorning on Tuesday, the storm was churning about 440km southwest of Tampa as it crept northward at 22 kph, carrying maximum sustained winds of 140kph.

Idalia is in line to become the fourth major hurricane to strike Florida over the past seven years, following Irma in 2017, Michael in 2018 and Ian, which peaked at Category 5, last September.

In Sarasota - a city hard-hit by Ian last year - Milton Bontrager's home is boarded up and stocked with food, water and a generator.

"I don't panic, I prepare," said Bontrager, 40, who runs six sport and charter fishing boats in Venice along the Gulf Coast near Tampa.

He stopped taking customers out days ago so he could secure the boats. His biggest craft is tied down to a floating dock with 16 lines and equipped with battery-powered pumps that turn on automatically if the boat starts taking on water.

From Tuesday through Thursday, Florida's Gulf Coast along with southeastern Georgia and eastern portions of North and South Carolina could face torrential rains of 10 to 20cm, the hurricane centre warned.

But Idalia's chief threat to human life stemmed from surging walls of seawater driven inland by high winds, inundating low-lying coastal areas, authorities said.

Surge warnings were posted for hundreds of miles of shoreline, from Sarasota to the sport fishing haven of Indian Pass at the western end of Apalachicola Bay.

In some spots, the surge of water could rise 2.5-3.7m, the hurricane centre said.

"The number 1 killer in all of these storms is water," Deanne Criswell, the Federal Emergency Management Agency's administrator, said on CNN on Tuesday.

St. Petersburg residents living in areas prone to flooding were urged to leave by Tuesday afternoon, the city's police chief Anthony Holloway said on CNN.

More than 40 school districts across the region canceled classes, DeSantis said. Tampa International Airport planned to suspend commercial operations beginning at midday Tuesday.

Some 5,500 National Guard troops were mobilised and between 30,000 and 40,000 electricity workers were standing by to help restore power quickly after the hurricane passes.

Brush with Cuba

As Floridians were scrambling for Idalia's arrival, Cubans were grappling with the aftermath of the storm, which lingered for hours on Monday near the western end of the Caribbean island nation, blowing off flimsy tin roofing, toppling trees and flooding coastal villages.

By Monday afternoon, brown floodwaters had swamped the small fishing village of Guan, an hour's drive south of Havana.

Decades-old buses missing floorboards and windows carried women and children to higher ground as winds howled, rattling tin roofs and slamming fishing boats tucked in the mangroves.

In Pinar del Rio, an area known for producing the tobacco used to make some of the world's finest cigars, 60% of the province was without power.

Authorities said the crops were largely protected, nearly a year after Ian devastated the local tobacco industry.

Resident Madelin Suarez Morejon said strong winds and rain persisted on Tuesday morning, but the damage was not comparable to Ian's.

"Fallen trees are blocking roads. There are power lines on the streets, which are covered with leaves and branches, and homes in many towns have lost roofs," she said. "Unfortunately, once again, it is a sad panorama for our city."

Authorities evacuated tens of thousands of people from that province as well as neighboring Artemisa, while squalls of heavy rain doused the Cuban capital of Havana.