Florence is being fed with warm water, rocket fuel for hurricanes, strengthening it to a category 4 storm, the most powerful to menace the region in nearly three decades as it barrels toward the Carolinas.
Nearly two million people have been issued an evacuation order as Mr Trump tweeted that this was "one of the worst storms to hit the East Coast in many years".
According to Reuters, Florence is packing winds of 140 miles per hour (220 kph), and is expected to grow even stronger before making landfall on Thursday, most likely in southeastern North Carolina near the South Carolina border, the National Hurricane Center in Miami said.
North Carolina Governor Roy Cooper told a news conference his state was in “the bull’s eye.”
Authorities warned of life-threatening coastal storm surges and the potential for Florence to unleash prolonged torrential rains and widespread flooding, especially if it lingers inland for several days.
NHC Director Ken Graham warned of “staggering” amounts of rainfall that may extend hundreds of miles inland and cause flash flooding across the mid-Atlantic region.
Forecasts expect 10 to 15 inches (25-38 cm) of rain in the hardest-hit areas, possibly more if the storm stalls over land, as expected, Graham said.
Classified as a Category 4 on the five-step Saffir-Simpson scale of hurricane strength, Florence was the most severe storm to threaten the U.S. mainland this year and the first of its magnitude to target the Carolinas since 1989, when Hurricane Hugo barreled over Charleston, South Carolina.
Hurricanes and cyclones