By Devika Krishna Kumar
TALLAHASSEE, Fla., Oct 10 (Reuters) - Hurricane Michael strengthened into a Category 4 storm early on Wednesday before it was expected to plow into Florida's Gulf shore with towering waves and roof-shredding winds as 500,000 people were under evacuation orders and advisories. Hurricane Michael was packing winds of up to 130 miles per hour (210 km per hour), hours before it was set to make landfall on Florida's Panhandle or Florida's Big Bend where it potentially could unleash devastating waves as high as 13 feet (4 meters), the National Hurricane Center (NHC) warned.
"THIS IS YOUR LAST CHANCE to evacuate before conditions start deteriorating within the next few hours," said Florida Governor Rick Scott in a Tweet early on Wednesday.
President Donald Trump declared a state of emergency for the entire state of Florida, freeing up federal assistance to supplement state and local disaster responses.
Michael gathered greater strength over warm Gulf of Mexico waters throughout the day on Tuesday as it jumped from a Category 2 to Category 3 on the five-step Saffir-Simpson wind scale.
The last NHC report said the fast-moving storm was about 180 miles (325 km) from Panama City, Florida.
Winds as strong as Michael is producing can inflict substantial damage to roofs and walls of even well-constructed homes, according to the National Weather Service.
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.
Hurricane-force winds extend about 45 miles from the center, with tropical storm-force winds reaching 175 miles, the NHC said.
The storm is likely to dump prodigious amounts of rain over Florida, Alabama and Georgia, as well as the Carolinas - still reeling from post-Florence flooding - and into Virginia. Up to a foot of rainfall (30 cm) is forecast for some areas.
The region should brace for "major infrastructure damage," specifically to electricity distribution, wastewater treatment systems and transportation networks, Jeff Byard, associate administrator for the Federal Emergency Management Agency (FEMA), told reporters on a conference call.
Byard said an estimated 500,000 people were under evacuation orders and advisories in Florida, where residents and tourists were fleeing low-lying areas in at least 20 counties stretching along 200 miles (322 km) of shore in the Panhandle and adjacent Big Bend region.
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.