What does rapid intensification mean? What to know as Hurricane Ian targets the US

There have been lots of uncertainties about Hurricane Ian’s track, but one thing about the storm has been consistent — weather forecasters have repeatedly said that rapid intensification will occur.

That means that Ian will be a major hurricane when it moves into the warm Gulf of Mexico and later targets the Florida coastline — including the Bradenton and Tampa areas — although the landfall location remains uncertain.

Manatee County, Florida has already issued a mandatory evacuation for residents who live in a zone that includes most areas along the county’s waterways.

Ian, a Category 1 hurricane at 11 a.m. EST Monday, has maximum sustained winds of 85 mph. Less than 24 hours ago, Ian was a tropical storm with winds of 45 mph.

Rapid intensification is defined by the National Hurricane Center as “an increase in the maximum sustained winds of a tropical cyclone of at least 30 kt in a 24 hour period.” Thirty knots equates to about 34.5 mph.

Ian is still in a period of rapid intensification.

“The intensity of Ian has increased by 30 kt during the past 18 hours,” the Hurricane Center said at 11 a.m. EST. “Further rapid intensification is expected during the next 24-36 hours as Ian crosses the high oceanic heat content of the northwestern Caribbean Sea within a very low vertical wind shear environment.”

The NHC said Ian will reach peak wind strength as a Category 4 hurricane in the Gulf in about 36 hours.

A satellite image of Hurricane Ian in the Caribbean sea nearing Cuba and the Gulf of Mexico.
A satellite image of Hurricane Ian in the Caribbean sea nearing Cuba and the Gulf of Mexico.

Hurricane-force winds are possible on the central Florida coast beginning Wednesday morning and heavy rainfall will spread to central and northern Florida Wednesday and Thursday.

Ian’s forward motion is forecast to slow as it moves just off the Florida coast, which the NHC says would likely prolong the storm surge, wind and rainfall impacts.

The NHC updates Ian’s track and wind speed every three hours. The next update occurs at 2 p.m. EST.

Sun Herald reporter Mary Perez contributed to this report.