Packing winds of up to 220 km/h (140 mph) late Monday, Florence was expected to further strengthen and become "an extremely risky major hurricane" by the time in makes landfall in the Carolinas on Thursday, the National Hurricane Center (NHC) said in a 21:00 UTC update.
Cooper and his counterparts in neighboring SC and Virginia ordered about 1 million people to evacuate coastal homes, including along the Outer Banks barrier islands.
By 11pm Monday (Tues afternoon NZT), Florence was centered about 1,745 kilometres east-southeast of Cape Fear, North Carolina, and moving west at 20 km/h.
US President Donald Trump signed declarations of emergency for both North Carolina and SC, freeing up federal money and resources for storm response. The current forecast track suggests the hurricane will most likely approach North Carolina or SC on Thursday as it gathers speed.
In a statement the centre said: "Further strengthening is anticipated, and Florence is expected to be an extremely risky major hurricane through Thursday". Panovich forecasts the storm will reach close to Category 4 status with the potential of 140 miles per hour winds.
"This one really scares me", U.S. National Hurricane Center Director Ken Graham warned. SC and North Carolina have ordered evacuations for people living in vulnerable areas along the coast. High winds will bring down trees and power lines, so residents are urged to be prepared to go without electricity for several days.
Meanwhile, games affecting Major League Baseball pennant races likely will be impacted by Florence.
It could weaken on Thursday, according to current predictions, but officials cautioned Florence will most probably remain "an extremely unsafe major hurricane through landfall". The forecast is for landfall to occur overnight Thursday into Friday morning.
According to CNN, weather experts say the storm is most likely to hit in the Carolinas.
Further east, forecasters are watching Hurricane Helene and Tropical Storm Isaac in the Atlantic, and a patch of showers in the western Caribbean, which has a 30 per cent chance of becoming a cyclone in the next 2 days. "Nonetheless, there still would be a very life threatening storm surge of somewhere around 10 to 15 feet".
There was little change in Florence's track during the 11 a.m. forecast from the National Hurricane Center.
The US president said he had spoken with governors of the threatened states, adding that the "federal government stands by, ready to assist 24/7".
As of 9 a.m. Tuesday, Hurricane Florence had maximum sustained winds of about 139 miles per hour and gusts of 167 miles per hour, said the National Hurricane Center.
Authorities in coastal towns have told residents to pick up sandbags and in North Carolina they are already preparing bulldozers and chain saws in case they are needed in any future clean-up and rescue operations.