Cruise ship gets tossed around by Hurricane Michael

Hurricane Michael is threatening more than 300 miles of the Gulf Coast, prompting emergency declarations in more than 100 counties from Mobile, Alabama through the Florida Panhandle and into the state's Big Bend region.

Residents in those areas are being warned to prepare for Michael to make landfall Wednesday as a "dangerous major hurricane," bringing damaging winds, and life-threatening storm surge and flash flooding.

"#HurricaneMichael isn't heading to any one town..." the National Weather Service tweeted Monday. "There are warnings for more than 300 miles of coastline. It's forecast to be a large and dangerous hurricane at landfall."

Michael underwent a period of "rapid intensification" from mid-day Sunday to mid-day Monday, growing from a tropical storm with sustained winds of 40 mph to a Category 1 hurricane with sustained winds of 75 mph.

What that means: A storm undergoes rapid intensification when its maximum sustained winds increase at least 35 mph in 24 hours or less, according to the National Hurricane Center. Michael is expected to undergo another rapid intensification in the next 24 hours.

The Category 1 hurricane now has maximum sustained winds of 90 mph, according to the National Hurricane Center.

The center said Michael could reach land as a Category 3 hurricane, with maximum sustained winds of at least 111 mph. Storms with winds of at least 111 mph are designated as "major" hurricanes.