Due to its enormous size, Hurricane Helene will likely be one of the strongest hurricanes to threaten our region so far this century.

If forecasts hold, the storm could stretch more than 400 miles wide by Thursday afternoon, with its center expected to pass about 125 miles off the coast of Tampa Bay toward landfall in the Panhandle.

More importantly, hurricane- and tropical-storm-force winds and rain from the eastern side of the asymmetric storm are expected to extend more than 250 miles (400 kilometers)—enough to feel the impacts across the entire Florida peninsula, which is no more than 140 miles (225 kilometers) wide.

Because of the larger than average size of Helene's forecast wind field, it would be stronger than 90 percent of hurricanes in the Gulf of Mexico over the past 20 years, the National Weather Service noted in a warning earlier this week.

“This size means that comparisons with previous hurricanes of similar strength and track to Helene do not provide a good prediction of what to expect in Tampa Bay,” said John Cangialosi, senior hurricane specialist at the National Hurricane Center.

Take, for example, Hurricane Idalia, which hit Florida's Big Bend region in 2023. Helene's path past Tampa Bay is very similar, Cangialosi said, and meteorologists expect the storms to have very similar intensity.

“But (Helene) will extend about 250 miles east of its center, while Idalia was about 150 miles, about average,” Cangialosi said. “So even if they follow the same trajectory with the same intensity, you'll still see much more noticeable effects because of that difference in size.”

“Helene is more similar in magnitude to Irma in 2017,” Cangialosi said. “But the difference for Tampa is that they were on the weak side of Irma this time and will definitely be on the strong side this time.”

Although there have been stronger storms since 2000, only a handful of them, including Irma, Ike, Ivan and Isidore, were larger than the strength Helene is forecast to reach.

“Every storm is a little different and those size parameters are quite different in this case,” Cangialosi said.

Cangialosi said Helene's size is particularly notable because of the storm surge. A storm surge warning is in effect for the Tampa Bay area, with floods of up to 8 feet (2.44 meters) forecast in Pinellas and Hillsborough and up to 12 feet (3.64 meters) in coastal Pasco County.

“The ultimate size of the storm is closely related to the impacts we are most concerned about in the Tampa Bay Area, which is storm surge,” Cangialosi said. “That is always the largest in areas like Clearwater and St. Pete and around Tampa, and that is important because there is a strong correlation and connection between the size and magnitude of the storm surge.”

Governor Ron DeSantis and Emergency Management Director Kevin Guthrie repeatedly emphasized Helene's magnitude during a press conference at a Tampa Electric Co. facility on Wednesday morning.

“It's a big, big storm,” DeSantis said, speaking of Helene's potential impact on Tampa Bay.

“Please do not focus on the forecast cone,” Guthrie said. “The dangers from this major storm, located over 250 miles from the center, will be widespread. … Tropical storm force winds will be felt up to 250 miles from the center. Tornadoes are likely.”

Tampa Bay Times data editor Langston Taylor contributed to this report.