Tropical Storm Helene is intensifying and is expected to strengthen into a major hurricane before slamming Florida’s Gulf Coast on Thursday with life-threatening storm surge, devastating winds and heavy rainfall.

Helene’s impact will not stop at the coast. Strong winds and flooding will also spread to parts of the southeast on Thursday night and Friday.

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Where is it now: Helene is centered 45 miles east-northeast of Cozumel, Mexico, and is moving northwest. Maximum sustained winds are 65 mph.

Rain from the storm is drenching parts of the Yucatan in Mexico and western Cuba. A few far-reaching rain bands have even spread as far as southern Florida.

Warnings and cautions in effect: A hurricane warning is in effect from Florida’s Big Bend to southwest Georgia, including Tallahassee. Storm surge warnings extend from Indian Pass south to Flamingo, including Tampa Bay and Charlotte Harbor.

Various tropical storm and hurricane watches and warnings are in effect for most other parts of Florida, northward into southern Georgia and southern South Carolina, as shown on the map below.

These warnings mean that hurricane, tropical storm, and storm surge conditions are expected (warnings) or possible (alerts) in these areas in the next 36 to 48 hours.

Stakeholders in warned areas should implement their hurricane plans and heed the advice of local emergency services.

Here’s the timeline:

-​ Wednesday: The center of Helene is closest to Cancun and Cozumel, bringing strong winds, storm surge, and heavy rain. Bands of heavy rain and strong winds will also continue to batter parts of western Cuba. Helene will eventually enter the southern Gulf of Mexico, where it will intensify and grow in size. A few high waves and outer rain bands will reach parts of Florida, and tropical moisture intercepting a front could wring heavy, flooding rain across parts of the Tennessee Valley from Georgia to eastern Tennessee.

-​ Thursday: Helene is expected to reach peak intensity in the eastern Gulf and then make landfall somewhere along the Florida Gulf Coast as a major hurricane Thursday night. While computer forecasting models suggest the most likely location for landfall is in the Big Bend or eastern Panhandle region of Florida, keep in mind that hurricane impacts (surges, wind, rain) often occur far from the center, especially in larger storms.

-​ Friday:Helene is moving rapidly northward through the Southeast toward the southern Appalachians and the Ohio Valley, bringing strong winds, flooding and rainfall, and a few tornadoes.

(Further strengthen your forecast with our detailed, hour-by-hour breakdown for the next 8 days – only available on our Premium Pro Experience.)

How strong can it get: Helene could become a major hurricane in the Gulf before making landfall.

That’s because heat content is a favorable ingredient for intensification, and the map below shows that there’s plenty of deep, warm water in the northwestern Caribbean Sea and parts of the Gulf of Mexico Loop Current. In fact, the Gulf of Mexico’s heat content is at a record high for this time of year, according to University of Miami tropical scientist Brian McNoldy.

Therefore, Helene could quickly become stronger and reach her highest intensity on Thursday.

Another factor to consider is wind shear. Wind shear typically limits or weakens tropical storms and hurricanes by tilting their circulation or blowing more thunderstorms away from the core.

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US Impact

Helene is expected to not only be a hurricane, but also to be large in size and able to move faster, both as it approaches the coast and as it moves further inland. As we discussed in a previous piece, that will affect the size and severity of Helene’s impacts.

Storm surge

The National Hurricane Center’s storm surge forecast is shown on the map below. As you can see, much of Florida’s Gulf Coast is expected to experience storm surge flooding, including areas as far south as the Keys.

The highest storm surge is expected along and east of where Helene’s center makes landfall. For now, that looks to be Florida’s Big Bend, Apalachee Bay, and Nature Coast. Some storm surge would 10 feet above ground level in these areas, especially if the peak surge arrives at high tide. For Cedar Key, that could be a record storm surge, easily several feet higher than Hurricane Idalia’s peak in August 2023 (6.84 feet).

Given Helene’s expected large wind field, significant storm surge flooding is also expected in the Tampa-St. Pete-Sarasota metro areas, which could exceed what was experienced over a year ago with Hurricane Idalia.

If you live near the coast, make sure you know where your evacuation zone is and follow any advice or orders from your local emergency response organization.

Winds

As previously mentioned, Helene will be both a large and fast-moving storm in the Gulf and then move inland, meaning that the strong winds will cover a larger area than normal.

Hurricane-force winds are not only possible along a stretch of Florida’s Gulf Coast in areas covered by hurricane warnings, but these strong winds could also push far inland into parts of northern Florida and extreme southern Georgia on Thursday night. Downed trees and power outages could be widespread in these areas, and even some structural damage is possible.

Tropical storm force winds will quickly spread along the west coast of Florida into the panhandle in the areas shown below Thursday through Thursday night. These tropical storm force winds could then move well inland into much of Georgia, eastern Alabama, and parts of the Carolinas Thursday night through Friday. Some downed trees and power outages are possible in these areas.

Precipitation

Helene will produce heavy rainfall along and east of its track this weekend, not only along the coast but also well inland to the southeast into the Ohio Valley.

The heaviest rain is expected Thursday through Friday across parts of the Southeast, but some bands of heavy rain are expected well before Helene Wednesday across parts of the Southeast, including the Atlanta metropolitan area. And some pockets of locally heavy rain could linger into Saturday across parts of the Ohio Valley and Florida.

Total rainfall could be 5 to 10 inches across the southeastern U.S., with isolated amounts of up to 15 inches possible. This rainfall could lead to flash flooding and river flooding.

Higher terrain in the southern Appalachians will be particularly susceptible to flooding and possible landslides. A rare “high risk” flood forecast has been issued by NOAA’s Weather Prediction Center from northeast Georgia to western North Carolina.

The increasingly moist soil in the southeast may make it easier for Helene’s winds to blow over trees.

Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite subjects. Contact him at X (formerly Twitter), Wires, Facebook And Blue sky.