Each line represents a computer model's best "guess" of where the center of the storm will go.
Parts of the Mid-Atlantic, especially from Virginia to Pennsylvania, have received 150 to 300 percent of their normal rainfall since May.
The major hurricane is expected to travel between Bermuda and the Bahamas on Tuesday and Wednesday before reaching the USA on Thursday.
The storm was still on a path to strike the Carolinas, potentially southern North Carolina, as a major hurricane at about 2 a.m Friday, according to the latest forecast from the hurricane center. ET, the National Hurricane Center (NHC) said in an advisory. The storm could impact anywhere from northern Florida to north of the Washington, D.C., area, producing life-threatening conditions. Mandatory evacuations have begun along North Carolina's coast.
Trump tweeted Monday afternoon that the federal government was monitoring the storm and was ready to help.
USA residents have been warned to prepare for the hurricane's impact.
Gov. Roy Cooper declared a state of emergency and is urging all North Carolinians to prepare. Vessel owners should make sure to check safety equipment is working and remove boats from the water or take them to safe harbor as the storm approaches.
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More than 1 million people along the Carolina coast fled toward higher ground on Monday in a mass evacuation ordered three days before the expected arrival of Hurricane Florence, a Category 4 storm and the most powerful to menace the region in almost three decades. The storm's maximum sustained winds are 65 miles per hour (100 kph) and it is moving west at 14 miles per hour (22 kph).
Its maximum sustained winds are at 105 miles per hour. It will affect the Cabo Verde Islands, possibly as a hurricane this weekend.
There are no coastal watches or warnings in effect at this time, but Met Service said strengthening is forecast during the next few days and Isaac is expected to become a hurricane by Monday. The storm is expected to take a track that will move west-southwest and eventually curve toward a possible landfall in North or SC.
"North Carolina is taking Hurricane Florence seriously, and you should, too", Cooper said. It would also mean a "massive rain event" from as far north as Virginia all the way down to SC.
States in the USA have been braced for there impact of the storm for several days. Before that, no major hurricane (Category 3 or greater) had arrived in the United States since 2005.
Maps of the storm's trajectory showed it likely to come ashore somewhere near the border of North Carolina and SC. Wherever it lands, it won't move much for three or four days, creating a storm surge and wind event, Osterberg said.
NHC added that the risk of direct impact from the storm along the U.S. East Coast over the next week has increased, but it is too soon to determine location, magnitude and timing of the impact.
Helene is the eighth named storm of the Atlantic hurricane season. People were told to prepare to evacuate communities up and down a stretch of coastline already identified as particularly vulnerable to rising sea levels due to climate change.