Hurricane Dorian was forecast to become an "extremely dangerous major hurricane" on Friday as it churned on its course to the Bahamas and the southeastern US over the next several days, according to the National Hurricane Center.
The storm posed "a significant threat" to the Bahamas and Florida and has maximum sustained winds near 110 mph, just one mile away from becoming a major Category 3 hurricane on the Saffir-Simpson hurricane wind scale, the centre said.
The storm was expected to continue strengthening as it headed toward the northwestern Bahamas and Florida peninsula, the centre said Friday.
As of midmorning Friday, Dorian was about 480 miles (772 km) east of the northwestern Bahamas and was expected to move over the Atlantic north of the southeastern and central Bahamas on Friday.
It was then expected to move near or over parts of the northwestern Bahamas on Sunday and be near the Florida peninsula late Monday, the centre said.
"Dorian is expected to become a major hurricane later today, and it will remain an extremely dangerous major hurricane while it moves near the northwestern Bahamas and approaches the Florida peninsula into early next week," the centre said.
A hurricane watch was in effect for the northwestern Bahamas. The storm has the potential to become an extremely dangerous Category 4 over the next several days and was forecast to reach top winds of up to 140 mph in the next 72 hours.
Dorian could be the first Category 4 or higher hurricane to make landfall on Florida's east coast since 1992 when Hurricane Andrew was blamed for 44 deaths in the state.
Anything at Category 3 or above is considered a major hurricane.
The centre said a life-threatening storm surge would raise water levels as much as 10 to 15 feet above normal tide in parts of the northwestern Bahamas, with "large and destructive waves" near the coast.
The storm was expected to produce 6 to 12 inches of rain, with isolated areas receiving as 18 inches in the northwestern Bahamas and coastal southeast United States.
Hurricane conditions were possible in the Bahamas by Sunday, the centre said."It's going to be this big, bad, intense storm — wherever it hits, it's going to do catastrophic wind damage," said Bill Karins, a meteorologist for NBC News.
"There is an increasing likelihood of a prolonged period of hazardous weather conditions that could last for a couple of days in parts of Florida early next week," the centre said.
Life-threatening storm surge and "devastating hurricane-force winds" along portions of Florida's east coast were likely by early next week, but it was too soon to determine where the hardest-hit areas would be, the centre said.
The storm was forecast to slow down near or over the Florida peninsula, leading to more days of wind, rain and storm surge, the centre said.
"A prolonged period of storm surge, high winds and rainfall is likely in portions of Florida into next week, including the possibility of hurricane-force winds over inland portions of the Florida peninsula," the centre said.
It is too soon to tell exactly when the storm would make its US landfall, but the hurricane centre warned of an increased likelihood of "life-threatening storm surge along portions of the Florida east coast late this weekend or early next week."
Six to 12 inches of rain is also expected in the US, with some areas getting up to 15 inches. The rainfall may cause flash floods.
Florida Governor Ron DeSantis has declared a state of emergency across the entire state. President Donald Trump called off his planned trip to Poland over the weekend to oversee the response to Dorian.
In a video posted from the White House on Thursday night, Trump said: "We're ready. We have the best people in the world ready, and they're going to help you."
Trump said that "somebody said" that Dorian would be "bigger or at least as big as Andrew," which caused more than $25 billion in damage in 1992.
Andrew was assessed as Category 5, with sustained winds of 175 mph. The National Hurricane Center says Dorian might reach Category 4, for which the wind range tops out at 156 mph.
The hurricane swept by the Virgin Islands and Puerto Rico as a Category 1 hurricane on Wednesday with few casualties and little confirmed damage.