The exact timing, location and magnitude of the storm's impacts on the US southeast coast in not yet clear but forecast tracks show it could make landfall along the Carolinas and southeast Georgia. The hurricane is registering maximum sustained winds near 130 miles per hour.
Florence, now a Category 4 storm on the five-level Saffir-Simpson hurricane scale, could approach the coast of SC or North Carolina on Thursday.
Florence is now projecting hurricane-force winds (74 mph and higher) up to 30 miles from its center.
"Florence has continued to rapidly strengthen", it said. Most other reports are using the word "catastrophic", in keeping with how the National Hurricane Center describes a Category 4 hurricane: "catastrophic damage will occur".
"Florence is. expected to remain an extremely unsafe major hurricane through Thursday", the hurricane center warned.
On North Carolina's Outer Banks, Dawn Farrow Taylor, 50, was gathering photos and important documents and filling prescriptions Monday before heading inland.
Florence had reached Category 3 strength earlier Monday, but data from hurricane hunter aircraft indicate the storm is quickly getting stronger as it moves over warm Atlantic waters.
The hurricane's impacts could range from a strong storm surge to flooding from torrential rainfall and hurricane-force winds. The hurricane is likely to bring unsafe surf and rip currents along the east coast.
North Carolina Governor Roy Cooper also urged his state's residents to get ready, noting the storm already was generating swelling waves and unsafe currents along the coast.
The European model paints the most aggressive forecast for central Georgia and shows wind gusts between 30 and 40 miles per hour for Sunday as the remnants of Florence drift to the south over SC.
In addition to flooding the coast with wind-driven storm surges of seawater as high as 12 feet (3.7 m), Florence could drop 20 inches to as much as 30 inches (51 cm to 76 cm) of rain in places, forecasters said. While Helene is forecast to slide out to sea away from land, Isaac is a very real threat in the Caribbean later this week, the hurricane center said.
South Carolina Emergency Management will open their emergency shelters on Tuesday based on need. "Normally, a landfalling tropical cyclone just keeps on going inland, gradually dissipating and raining itself out".
Once the storm hits the North Carolina coast, Campbell said the slow moving system could cause significant flooding in addition to hurricane force winds.
Florence is one of three hurricanes in the Atlantic Ocean, along with Helene and Isaac.