He said the chances are small that Dorian would still be a hurricane when it reaches Columbia, but that will be determined by its movement in the next three days.
While Puerto Rico's east end saw heavy rain from the storm's outer bands, the main part of the island remained largely unaffected, easing concern Dorian might further devastate an island still recovering from Hurricane Maria's 155 miles per hour winds in 2017.
Leaving mercifully little damage in its wake in Puerto Rico and the Virgin Islands, a strengthening Hurricane Dorian posed an increasing menace to Florida on Thursday as it swirled toward a possible direct hit on the state over Labor Day weekend. "The more we hear about this storm, it sounds like a serious one".
"If it makes landfall as a Category 3 or 4 hurricane, that's a big deal", he said.
They warned, too, that Dorian was moving more slowly, which could subject the state to a prolonged and destructive pummeling from wind, storm surge and heavy rain.
Earlier in the day, Dorian ploughed through the US Virgin islands and Culebra, an island belonging to Puerto Rico, data from the National Hurricane Centre (NHC) showed.
Category 3 hurricanes produce sustained winds of 111 miles per hour to 129 miles per hour, which can easily uproot trees and cause devastating structural damage.
Trump declared a state of emergency in Florida and authorized the Federal Emergency Management Agency to coordinate disaster-relief efforts. The storm is forecast to pass east of the Bahamas and approach Florida's Atlantic Coast late Sunday or Monday.More news: Oil Extends Gains Buoyed By US Stock Drawdown
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Because Dorian could impact Florida's Kennedy Space Center, NASA has said it will have a crawler-transporter move NASA's mobile launcher Friday from launch pad 39B to the Vehicle Assembly Building about 3.5 miles away.
"We are grateful that it wasn't a stronger storm", he said.
Officials such as Florida Gov. Ron DeSantis have urged people to have seven days of food and medicine available - and coastal residents already are stripping store shelves bare with Dorian in mind.
Wind speed probabilities for Hurricane Dorian as it makes its way towards the United States coast.
At the Kennedy Space Center at Cape Canaveral, NASA chose to move indoors the mobile launch platform for its new mega rocket under development. The Hurricane Center is warning those living in the southeast and the Caribbeans of possible life-threatening flash floods.
But as it passed Puerto Rico, the storm was blowing winds far less strong than when Hurricane Maria hit in September 2017. "We can get a better track after it makes landfall".
One man died after falling from the roof of his house while cleaning a drain in preparation for the storm, Puerto Rico Public safety Secretary Elmer Roman said.
Trump, who approved an emergency declaration for the island late on Tuesday evening, fired off a verbal broadside against Puerto Rico's leaders on Twitter early on Wednesday. We'll have a clearer picture Friday into Saturday as we trend closer to the actual event.