Tropical Storm Ian forecast to impact Florida as major hurricane

A tropical storm that is currently on track to make landfall in Florida next week as a hurricane could strengthen into a Category 4 storm, the latest forecast shows.

Tropical Storm Ian formed over the central Caribbean Sea late Friday, becoming the ninth tropical storm of the season.

The storm is expected to continue to strengthen over the weekend into a hurricane by Sunday night as it approaches the Cayman Islands. A hurricane watch is currently in effect for the Cayman Islands.

Ian is forecast to strengthen into a Category 2 hurricane as it closely passes the Cayman Islands, then become a major Category 3 hurricane early Tuesday as it moves past Cuba. Very warm ocean waters and low wind shear are providing favorable conditions for rapid intensification of the storm, which is projected to become a Category 4 storm by Tuesday afternoon.

The current forecast track shows landfall on the west coast of Florida or the Florida Panhandle by midday Thursday, though the track and intensity of the storm can still change over the coming days. Increased wind shear could help weaken Ian before it makes landfall, though it is still too early to determine by how much.

"With majority of west coast in the cone, uncertainty of landfall remains high," the National Weather Service said.

The National Hurricane Center has advised residents of Cuba, the Florida Keys and the Florida peninsula to have a hurricane plan in place and closely follow forecast updates.

In preparation for the storm, Florida Gov. Ron DeSantis issued an executive order Friday declaring a "state of emergency" for 24 Florida counties in the system's potential path. He expanded the order on Saturday to include the entire state of Florida, with conditions "projected to constitute a major disaster."

"This storm has the potential to strengthen into a major hurricane and we encourage all Floridians to make their preparations," DeSantis said in a statement. "We are coordinating with all state and local government partners to track potential impacts of this storm.”

The emergency order means members of the Florida National Guard will be activated and on standby.

White House officials confirmed late Friday that FEMA Administrator Deanne Criswell had spoken to DeSantis about the pending storm.

ABC News' Riley Winch, Melissa Griffin and Dan Amarante contributed to this report.