Robbie Berg, a hurricane specialist at the National Hurricane Center advises, "There is a real possibility that Michael will strengthen to a major hurricane before landfall".
An unidentified man in the Florida Panhandle was killed by a fallen tree when it ripped through his home's roof, a spokeswoman for the Gadsden County Sheriff's Office told Fox News. "The historical record, going back to 1851, finds no Category 4 hurricane ever hitting the Florida panhandle". Tropical storm conditions are expected in the warning area along the southeast US coast by Wednesday, and possible in the watch area by late Wednesday.
More than 380,000 homes and businesses in Florida were without power at the height of the storm.
"If you decide to stay in your home and a tree falls on your house or the storm surge catches you and you're now calling for help, there's no one that can respond to help you", Morgan said at a news conference.
"The wind that came through here was surreal". Gulf County in the Panhandle of Florida. "It's unlivable. It's heartbreaking".
Cameras outside the International Space Station captured video of Michael as the storm continued churning over the Gulf of Mexico. Data from a NOAA Hurricane Hunter aircraft indicate that maximum sustained winds have increased to near 125 miles per hour (205 km/h) with higher gusts.
The storm then looks destined to move through the southeast USA on Thursday as a tropical storm, bringing heavy rains to Georgia and the Carolinas, before moving back out to the Atlantic on Friday. Forecasters said tornadoes could be spun off by the storm, and 3 to 6 inches of rain could cause flash floods as it barrels over a corner of the country still recovering from Hurricane Florence.
At 2 p.m. Tuesday, the National Hurricane Center said Michael had top sustained winds of 110 miles per hour (175 kph).
Parts of western Cuba, which was hit by the storm on Monday, were forecast to receive up to a foot of rain.
Television news footage showed homes submerged in floodwaters up to their roofs in Mexico Beach.
Updates, tracking resources as storm makes landfall
It appeared to be so powerful that it was expected to remain a hurricane as it moved into Alabama and Georgia early Thursday. Jason Phipps looks through his family's roofless apartment after Hurricane Michael made landfall in Panama City, Fla.
It swamped streets, bent trees, stripped away limbs and leaves, knocked out power, shredded awnings and sent other building debris flying.
Bill Manning, a 63-year-old grocery clerk, fled his camper van in Panama City for safer quarters in a hotel only to see the electricity there go out. "I didn't expect all this", he said. For a depiction of areas at risk, please see the National Weather Service Storm Surge Watch/Warning Graphic, available at hurricanes.gov.
Forecasters say Hurricane Michael is intensifying as it takes direct aim to strike Florida sometime Wednesday. Wind damage was also widespread.
Damage in Panama City near where Michael came ashore on Wednesday afternoon was so extensive that broken and uprooted trees and downed power lines lay almost everywhere.
The Florida governor called Michael "a monstrous storm" and urged residents to listen to officials.
After daylight Thursday residents of north Florida would just be beginning to take stock of the enormity of the disaster. Cuban authorities said they evacuated about 400 people from low-lying areas.
"It's very chaotic", broker and owner of Parker Realty of Mexico Beach told WJHG/WECP. "This happened so quickly", he said. It was the most powerful hurricane to hit the continental U.S.in almost 50 years and at least one death was reported during its passage.
The storm is expected to make landfall on Wednesday.
Trump issued an emergency declaration for Florida, freeing up federal funds for relief operations and providing the assistance of FEMA, which has more than 3,000 people on the ground.
The governors of Florida, Alabama and Georgia declared states of emergency as Michael closed in, and hundreds of Florida National Guard members were activated. We will continue to monitor Hurricane Michael's path and GEMA/HS is leading our preparedness efforts.