With maximum sustained winds of 140 miles per hour (220 kph), Florence was due to grow even stronger before making landfall on Thursday, mostly likely in southeastern North Carolina near the SC border, the National Hurricane Center in Miami said.
The current forecast track predicts that Florence will approach the southeast USA coast on Thursday. Drawing energy from the warm water, it could have top sustained winds of 130 miles per hour (209 kph) or more by Tuesday, the Miami-based National Hurricane Center said.
Meanwhile, behind Florence is Hurricane Isaac, which had maximum sustained wins at 75 mph and was centered about 1,150 miles east of the Windward Islands, moving west at 14 mph.
In a news conference Sunday, South Carolina Gov. Henry McMaster urged residents to begin making preparations before the storm hits. "This storm gets stronger and stronger" and is on its way to a head-on impact on the Carolinas, CNN meteorologist Chad Myers said.
The storm's winds grew by 35 miles-per-hour in the last 24 hours, and Florence is forecast to reach Category 4 status, one step short of the the most severe level, with 150 mile-per-hour winds by Wednesday.
At this height of the Atlantic hurricane season, Florence was being trailed on east-to-west paths by two other hurricanes, Helene and Isaac.
Heavy rain and potential flooding and mudslides are a growing concern, more so than winds.
Rainfall amounts could be measured in feet over part of the Carolinas and Virginia, which could lead to major and even life-threatening flooding.
Florence was a Category 4 storm late afternoon Monday. "I plan to do most of my cooking on the grill".
Hurricane Florence is plowing toward the East Coast as a Category 4 storm with a 500-mile wing span, forcing dire warnings and mandatory evacuations - including the entire coastline of SC and parts of Virginia and North Carolina.
But Hurricane Center officials warned that anyone in coastal and inland locations from SC to the mid-Atlantic region should "closely monitor the progress of Florence, ensure that they have their hurricane plan in place, and follow any advice given by local officials".
The Atlantic hurricane season has picked up in earnest: There are three tropical systems worth tracking across the Atlantic. Plenty of moisture in the atmosphere turned into daily storms that became pretty widespread both Saturday and Sunday.
Red flags flying on beaches warned swimmers to stay out of waters as seas began kicking up. SC emergency management officials said they were "preparing for the possibility of a large-scale disaster".
Myrtle Beach hardware stores and supermarkets were busy ringing up sales of bottled water, plywood and generators. However, we will likely see impacts here in the Valley as well.
The US Navy ordered ships at its major base in Hampton Roads, Virginia, to put to sea, saying "the forecasted destructive winds and tidal surge are too great to keep the ships in port".
Florida-based Carnival Cruise Line was re-routing its cruise ships, but there were other hurricanes to contend with. The University of North Carolina Wilmington announced it has canceled classes and issued a voluntary evacuation for students starting at noon today.