Potential hurricane could hit Gulf Coast this week: What to know about Storm Helene

Florida is bracing for what could be the United States' heaviest-hitting hurricane so far this season, as an area of thunderstorms builds strength in the Caribbean Sea before potentially bringing life-threatening storm surge and hurricane-force winds to the Southeast later this week.

The system will pick up pace and is expected to rapidly intensify into Hurricane Helene as it approaches the coast, hurling wind, rain and storm surge further into the southeast before making an expected landfall in Florida, said the National Hurricane Center, which has dubbed it Potential Tropical Cyclone Nine.

Florida Gov. Ron DeSantis has declared an emergency for 41 the state's 67 counties in an effort to expedite preparations and coordination between the state and local governments ahead of the storm's impacts.

With little time to prepare, Tampa General Hospital began erecting a 10-foot-high flood barrier around the facility Monday because of the chance for storm surge and shifts in the storm's track.

On Monday, the potential cyclone was a mass of showers and thunderstorms churning in the far western Caribbean Sea. The NHC predicts that the system will rapidly intensify, likely becoming a hurricane by Wednesday night and eventually reaching Category 3 strength.

The last storm to make landfall in the US as a Category 3 hurricane - Idalia - also came ashore in Florida, packing winds of 125 mph and generating record-breaking storm surge from Tampa to the Big Bend in August last year.

Idalia went through a period of rapid intensification over the warm waters of the Gulf of Mexico - with its sustained winds increasing 55 mph over the course of 24 hours.

A tropical storm watch was raised Monday afternoon for Florida's Dry Tortugas and part of the Keys and Monday evening for Bonita Beach to Flamingo, where a storm surge watch is also in effect.

Additional alerts will be issued for the US in the coming days, with a potential landfall in Florida expected perhaps as soon asThursday evening.

The National Hurricane Center is showing a landfall in Florida's Big Bend region, but CNN meteorologist Mary Gilbert says anyone from Florida's Gulf Coast to eastern Louisiana should be on alert this week.

Strong, potentially damaging winds and storm surge are likely near where the system ultimately comes ashore. The system will also churn up seas in the Gulf and could produce rough surf and dangerous rip currents for much of the basin, especially later this week.

"Strengthening is expected during the next few days, and the system is forecast to become a hurricane on Wednesday and continue strengthening on Thursday as it moves across the eastern Gulf of Mexico," the NHC said in an 11 p.m. advisory Monday.

Confidence in the system's exact track will increase after it forms, since forecast models struggle to accurately pinpoint where it could go without a center to lock onto.

This stormy weather will drop potentially flooding rainfall over portions of Central America, Mexico, Cuba and Jamaica as it tries to organize into a tropical system. Hurricane and tropical storm watches are already in effect for parts of Mexico and Cuba.

"Potential Tropical Cyclone Nine will bring heavy rain to portions of the western Caribbean, which will cause considerable flooding and mudslides across western Cuba," the National Hurricane Center said.

In its Monday 5 p.m. ET forecast discussion the NHC warned that the system's expansion over the record-warm Gulf of Mexico would have far-reaching impacts for the US.

The "storm surge, wind, and rainfall impacts will extend well away from the center, particularly to the east of the system. In addition, the fast forward speed as it approaches the coast will likely result in farther inland penetration of gusty winds over parts of the southeastern United States after landfall," it said.

Heavy rainfall is possible for much of the Southeast starting around midweek. A level 2 of 4 risk of flooding rain is in place for much of Florida, Georgia, Alabama and parts of the Carolinas Thursday, according to the Weather Prediction Center.

Helene could also bring strong winds and torrential rainfall to much of Georgia and the Carolinas by Friday. This could lead to dangerous flooding and significant power outages.

"Heavy rainfall will likely result in locally considerable flash and urban flooding across portions of Florida, with isolated flash and urban flooding possible across the Southeast, Southern Appalachians, and the Tennessee Valley Wednesday through Friday. Minor to isolated moderate river flooding will be possible," the National Hurricane Center said.

Helene would be the fourth hurricane to make landfall in the US this year and the fifth hurricane to slam Florida since 2022.

The repeated blows have pushed Florida's insurance market to the brink, with insurers pulling out of the state because of the increasing risk of extreme weather due to climate change.

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