(Reuters)

Tropical Storm Debby is expected to gather strength and become a hurricane on Sunday night (August 4), the US National Hurricane Center (NHC) said, rather than Monday, as it had forecast just hours before.

Forecasters expect a large number of Atlantic hurricanes in the 2024 season, which began on June 1, with four to seven seen as major, among 25 named storms. That exceeds the 2005 record-breaking season that spawned hurricanes Katrina and Rita.

Preparing for Debby, Governor Ron DeSantis called up 3,000 National Guard and placed most of Florida’s cities and counties under emergency orders, while evacuations were ordered in parts of the Gulf Coast counties of Pasco Hernando and Citrus.

“It’s become clearer and clearer that Debby will become a hurricane before it makes landfall,” said Jamie Rhome, deputy director of the National Hurricane Center, urging people to heed the evacuation orders.

The agency revised its forecast at 2:00 am Eastern Daylight Time (EDT) for Debby, which had become a named tropical storm late on Saturday after spending days as a broad, sloppy system in the Atlantic.

As of 11:00 am EDT (3:00 pm GMT), Debby was crawling at 20 kilometres/hour into the Gulf Coast about 210 kilometres southwest of Tampa, packing maximum sustained winds of nearly 100 kilometres/hour with higher gusts, as it gains strength to become a hurricane.

The centre of Tropical Storm Debby will move across the eastern Gulf of Mexico through Sunday and reach the Florida Big Bend coast Monday morning, the NHC said in its latest advisory on Sunday.

Debby is then expected to move slowly across northern Florida and southern Georgia on Monday and Tuesday, the NHC said.

It had left Cuba’s northern coast on Saturday evening when it was about 100 miles (160 km) west-southwest of Key West in Florida, the NHC added.

“This is a life-threatening situation,” the NHC said in a report. There were “a host of hazards, not just the wind,” Rhome added.

He warned of storm surges up to seven feet (two metres) along Florida’s Big Bend area, where Debby is expected to hit just southeast of the peninsular state’s Panhandle.

“Now, I stand at six feet tall,” Rhome said. “So that’s over my head.” Heavy rain of 10 inches (25 cm) could be expected, increasing to 15 inches (38 cm) in some areas, and more if the storm slowed or stalled over land, he added.

Debby is expected to lose some strength after landfall but bring heavy rain as it crosses central Florida out to the Atlantic coast, before crawling up to Savannah, Georgia, and then onward to Charleston, South Carolina, early in the week.

Ocean surges forecast for Bonita Beach northward to Tampa Bay could send sea waves further inland than normal, damaging structures and endangering anyone in their path.

A tropical storm warning is in effect for extreme southern Florida, stretching as far north as the Fort Myers area crushed by Hurricane Ian in 2022.

Debby is expected to take a similar track as Hurricane Ian, which killed 103 people in Florida and caused damage running into billions of dollars as it barrelled along the Gulf Coast.

Only one hurricane, Beryl, has yet formed in the Atlantic this year. The earliest Category 5 storm on record, it ravaged the Caribbean and Mexico’s Yucatan peninsula before rolling up the Gulf Coast of Texas as a Category 1 storm, with winds up to 95 mph (153 kph).