Helene is expected to be one of the strongest hurricanes in the last 20 years | Hurricane Center

Tropical Storm Helene is expected to become one of the largest — though not necessarily strongest — hurricanes of the past two decades as it moves through the Gulf of Mexico this week, with impacts extending “farther than normal” beyond the storm's eyewall, according to forecasts from the National Hurricane Center in Miami.

Helene formed as a tropical storm in the Caribbean on Tuesday morning with winds of 45 mph (72 km/h). The storm is expected to strengthen significantly over the eastern Gulf of Mexico and reach the eastern edge of the Florida Panhandle or Big Bend region as a major hurricane on Thursday evening.

While the storm's track and intensity will likely change somewhat before it reaches land, NHC meteorologists said one factor seems unavoidable: its size.

“Predicting the strength of the storm will be a challenge,” said John Cangialosi, senior hurricane specialist at the NHC, “but we're actually pretty confident it's going to be big.”

In a 10 a.m. update Tuesday, the NHC predicted Helene's winds would cover an area equivalent to the 90th percentile of hurricanes at similar latitudes. Cangialosi said meteorologists used 20 years of storm data to make that assessment.

This means that if the forecast comes true, Helene would be larger than about 90 percent of all other storms of the last 20 years.

“Much bigger than average”

Cangialosi said Helene's forecast strength is comparable to catastrophic storms such as Hurricane Irma, which hit Florida at intensity 4 in 2017, and Hurricane Katrina, which devastated New Orleans after making landfall in Louisiana as a Category 3 storm due to catastrophic levee failures.

Regardless of Helene's intensity, its “much larger than average” circumference is expected to bring severe storm surge, wind and rainfall to areas well outside its center, particularly on the eastern side where more intense impacts are likely.

If Helene's path follows the NHC's latest forecast, Cangialosi said, “most of Florida will be on the dirty side.”

Aside from dangerous sea conditions in the Gulf, Helene is not expected to have any direct impact on Louisiana, according to the National Weather Service in New Orleans.

Not the same as Idalia

While Helene is currently expected to take a similar path to Hurricane Idalia, which hit Florida's Big Bend region as a Category 3 storm in 2023, Cangialosi said NHC meteorologists don't want people to think Helene will have the same impact. Helene, he said, is expected to be significantly larger.

While Idalia left much of Florida's west coast unscathed, including the Tampa Bay area, the same is not expected for Helene. As of 10 a.m. Tuesday, Helene was forecast to produce a storm surge of 10 to 15 feet across much of the Big Bend region, 5 to 8 feet in the Tampa Bay area, and 3 to 5 feet in Charlotte Harbor. A storm surge of 1 to 3 feet was expected as far south as the Florida Keys.

Helene is expected to accelerate before reaching land, and this rapid forward motion as it crosses the coast should result in strong winds far inland over parts of the southeastern United States, according to the NHC. Widespread power outages, damage to critical infrastructure, and road blockages are possible near and far from the center of the storm.

“I know this is not good news,” Cangialosi said. “But we really want to spread the message.”

Cangialosi said Florida residents should focus primarily on the watches and warnings issued for their areas, which take into account the forecast size of the storm.