"When high winds and low pressure cause water to amass inside the storm, they release a powerful rush over land when the hurricane moves onshore", CoreLogic said in a statement.
About 3.7 million people are under hurricane warnings - in the Panhandle and Big Bend regions as well as parts of southeastern Alabama and southern Georgia.
Hurricane-force winds extend outward up to 45 miles (75 km) from the center and tropical-storm-force winds extend outward up to 175 miles (280 km). The wind speed was just one miles per hour short of Category 3 status.
He declared a state of emergency for 35 Florida counties from the Panhandle to Tampa Bay, activated hundreds of Florida National Guard members and waived tolls to encourage those close to the coast to evacuate inland. Anticipated landfall is expected Wednesday on the northeast Gulf Coast, where authorities warned of a potentially devastating strike.
Both NOAA and Air Force Reserve Hurricane Hunter aircraft have flown through the hurricane's four quadrants - and the NHC says, "The planes actually passed through the eye around the same time [Tuesday morning], and reported that they could see one another". The system has now graduated to Category 2 hurricane status and is expected to reach Category 3 (with winds in excess of 110 mph) when it makes its US mainland landfall on Wednesday afternoon.
Michael gained new strength over warm tropical waters amid a forecast that it would swiftly intensify into a major hurricane before striking Florida's northeast Gulf Coast, where frantic coastal residents were boarding up homes and seeking evacuation routes away from the risky storm heading their way.
A hurricane warning is in effect from the Suwannee River on Florida's Gulf Coast west to the Alabama / Florida line.
"This storm will be life-threatening and extremely unsafe", Scott said Sunday US time after receiving a briefing at the State Emergency Operations Centre.
Some 120,000 residents were under mandatory evacuation orders in Bay County in the panhandle, a low-lying area of beachfront resorts and retirement communities. A tropical storm watch was also issued for the eastern coasts of Georgia and SC.
"Minimal impact" is a lousy title for an action film but a good prediction for a hurricane, and that's what Storm Team 4 meteorologist Lauryn Ricketts said was coming to the D.C. area.
Yes, really, some of that tide going on just adds some more water to the whole situation, because when we really look at this, we have the rainfall threat, of course, that we have been looking at, but look at these values related to your question.
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Tallahassee´s Democratic Mayor Andrew Gillum, who is campaigning to succeed Scott as governor in next month´s elections, suspended his campaign and returned to the state capital to oversee storm preparations.
"We (first) bumped it up to Tuesday night. and then we bumped it up to Tuesday morning", Cindy Guinn said.
Some parts of Florida could see storm surges of nine to 13ft and up to a foot of rain.
Scott has declared a state of emergency in 35 counties in Florida.
In Panama City Beach, many businesses were closed and homes boarded up.
"Since 6 a.m.it's been backed up. We're just now running out of regular (gasoline)", Danny Hess, an employee at a gas station in Panama City, told local WJHG television. Winds will be less than 20 miles per hour for the northern half of the state as the main impact comes across southeast Alabama.
At least 57,000 coastal homes, as well as high-rise condos and businesses, will be at risk from the landfall of Hurricane Michael.
Michael has been lashing western Cuba as it churned toward the United States.
Heavy rain at the weekend caused 13 deaths in Central America after Michael formed off the coast of northern Honduras.
The governor's office cautioned that flash flooding and tornadoes are possible with any hurricane.