Michael is now centered about 360 miles south of Panama City, Florida, and landfall is likely to occur sometime around midday Wednesday between the Florida Panhandle and the state's Big Bend. It is forecast by the National Hurricane Center to become a Category 3 storm before coming ashore on Wednesday in either the Panhandle or Big Bend area of the state.
As a result, the northeastern Gulf Coast is undergoing mandatory evacuations - that includes the Florida Panhandle (stretching into Big Bend) as well as parts of southeast Alabama and southern Georgia.
A hurricane hunter plane that bounced into the swirling eye of Michael off the western tip of Cuba late Monday found wind speeds were rising even as forecasters warned the storm could reach major hurricane status with winds topping 111 miles per hour (179 kph) by Tuesday night.
The last major hurricane - Category 3 or above - to hit the Panhandle was Hurricane Dennis, which made landfall near Pensacola in 2005, according to hurricane center data.
Tuesday afternoon, President Donald Trump approved an emergency declaration for Florida.
Among them was Betty Early, 75, a retiree who joined about 300 fellow evacuees huddled on makeshift bedrolls of blankets and collapsed cardboard boxes at an elementary school converted into an American Red Cross shelter in Panama City, near the storm's expected landfall. "I'm blessed to have a place to come", she told Reuters.
He said: "You can not hide from storm surge".
"Historically, hurricanes that approach the Florida coast in this area tend to weaken slightly prior to landfall, but little difference in impact related to wind and storm surge is likely regardless", Kottlowski said. The hurricane center said the storm could dump as much as 30 centimeters (12 inches) of rain, potentially triggering flash floods and mudslides in mountainous areas.
The Gulf of Mexico produces 17 percent of daily US crude oil output and 5 percent of daily natural gas output, according to the US Energy Information Administration.
About 2,500 National Guard troops were deployed to assist with evacuations and storm preparations, and more than 4,000 others were on standby. In Georgia, Gov. Nathan Deal declared a preemptive state of emergency for 92 counties. Some 17,000 utility restoration workers were also on call. At that strength, it would rank as the most powerful storm to strike the Panhandle in more than a decade. The storm could inundate more than one-fourth of that coast's dunes, causing flooding behind the protective dune line, said Kara Doran, leader of the USGS Coastal Change Hazards Storm Team.