"Maximum sustained winds…90 Mph…150 Km/H," the center said in its fresh advisory.
According to NHC, as of 06:00 GMT, the storm was about 80 kilometers (50 miles) of the city of Morehead, the US state of North Carolina.
The agency also noted that "catastrophic freshwater flooding was expected over portions of North and South Carolina."
More than 10 million people are believed to be in the path of Hurricane Florence. The disaster triggered the introduction of the state of emergency in Washington D.C. as well as the state of North and South Carolina, Virginia and Maryland.