The enormous size of Hurricane Helene likely makes it one of the largest hurricanes to threaten our region so far this century.

If forecasts hold, the storm could stretch more than 400 miles by Thursday afternoon, with its center expected to pass 125 miles offshore from Tampa Bay toward the Panhandle.

More importantly, hurricane and tropical storm force winds and rainfall from the eastern side of the asymmetric storm are expected to extend over an area of ​​250 miles, enough to feel the effects across the entire Florida peninsula, which is up to 140 miles wide.

The above-average size of Helene’s forecast wind field would make it larger than 90 percent of Gulf of Mexico hurricanes in the past 20 years, the National Weather Service said in an alert earlier this week.

According to John Cangialosi, senior hurricane specialist at the National Hurricane Center, comparisons to previous hurricanes of similar strength and path to Helene are not a good indication of what we will see in Tampa Bay.

Take Hurricane Idalia, for example, which hit Florida’s Big Bend region in 2023. Cangialosi said Helene’s path through Tampa Bay is much the same, and meteorologists expect the storms to be of similar intensity.

“But (Helene) will extend about 250 miles east of the center, where Idalia was about 150 miles, about average,” Cangialosi said. “So even if they take the same path with the same intensity, you’re still going to see much more noticeable effects because of that size difference.”

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

Although there have been more powerful storms since 2000, only a few, including Irma, Ike, Ivan and Isidore, have grown larger than Helene’s expected size.

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

Cangialosi said Helene’s size is most noticeable because of its storm surge. The Tampa Bay area is under a storm surge warning, with a predicted surge of up to 8 feet in Pinellas and Hillsborough, and as much as 12 feet in coastal Pasco County.

“The ultimate size of the storm is just super tied to the impact that we’re most concerned about for the Tampa Bay area, which is storm surge,” Cangialosi said. “That’s always the greatest for areas like Clearwater and St. Pete and around Tampa, and that’s important because there’s a strong correlation and connection between the size and the amount of surge.”

Gov. Ron DeSantis and Emergency Management Director Kevin Guthrie emphasized Helen’s magnitude several times during a news conference at a Tampa Electric Co. plant Wednesday morning.

“It’s a very, very big storm,” DeSantis said as he discussed Helene’s potential impact on Tampa Bay.

“Please do not focus on the forecast cone,” Guthrie said. “The hazards from this large storm, more than 250 miles from the center, will be far reaching. … Tropical storm force winds may be felt 250 miles from the center. Tornadoes are likely.”

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