At 8 a.m. EDT, Michael was centered was about 90 miles (145 kilometers) from Panama City and Apalachicola, moving fast at 13 mph (21 kph). A Tropical Storm Watch is in effect from Chassahowitzka to Anna Maria Island, Florida, including Tampa Bay; from the Mississippi/Alabama border to the Mouth of the Pearl River; from Surf City, North Carolina to Duck, North Carolina, and for the Pamlico and Albemarle Sounds. The storm was packing maximum sustained winds of 145 miles per hour, making it a strong category four system on the Saffir-Simpson hurricane wind scale.
On a full-throttle journey from the Gulf of Mexico, Michael will bring "life-threatening" storm surge, hurricane-force winds and torrential rainfall after developing from a seemingly minor tropical storm off Mexico's Yucatan Peninsula.
NHC Director Ken Graham said Michael represented a "textbook case" of a hurricane system growing stronger as it drew near shore, in contrast to Hurricane Florence, which struck North Carolina last month after weakening in a slow, halting approach.
"Should Michael's eye cross the coast as a Category 4 hurricane, it would be the first time on record for such an occurrence over the Big Bend area of Florida's coast", AccuWeather senior meteorologist Alex Sosnowski said.
"You're going to see roofs off houses".
Numerous buildings in Panama City were demolished or left without roofs amid deserted streets littered with debris, twisted, fallen tree trunks and dangling wires. In the meantime, curfews were imposed across much of the region. "I didn't expect all this", he said. "Hopefully more people will leave".
The short-term rental company announced Tuesday that homes in Florida, Georgia and Alabama will host guests for free from October 8 to 29.
And people living far away from the center of the hurricane aren't immune.
While Florence wrung itself out for days and brought ruinous rains, fast-moving Michael is likely to be more about wind and storm surge.
"There are so many downed power lines and trees that it's nearly impossible to get through the city", Apalachicola Mayor Van Johnson said.
Officials urged residents to heed evacuation orders, particularly in coastal areas where some mandatory evacuations are already under way. Schools and state offices in the area will be shut this week.
"Those who stick around to experience storm surge don't typically live to tell about it unfortunately", he said.
He was one of about 2,500 of the town's 3,500 residents who ended up staying put, many of them caught off guard by the storm's rapid escalation as it approached.
"This situation has NEVER happened before", it said on Twitter.
"Unfortunately, this is a hurricane of the worst kind", said Brock Long, head of the Federal Emergency Management Agency.
"Satellite images of Michael's evolution on Tuesday night were, in a word, jaw-dropping", wrote Bob Henson, a meteorologist with weather site Weather Underground.
On its current track, the core of Michael is expected to move northeastward across the southeastern US on Wednesday night and Thursday, and then move off the Mid-Atlantic coast away from the United States on Friday.
Michael's barometric pressure at landfall was 919 millibars, by that measurement the third-strongest hurricane to hit the USA on record, trailing on the 1935 Labor Day Hurricane and Hurricane Camille in 1969.
The home to the 325th Fighter Wing and some 600 military families appeared squarely targeted for the worst of the storm's fury, and leaders declared "HURCON 1" status, ordering all but essential personnel to evacuate.