The local authorities declared the state of emergency across North Carolina, South Carolina, and Virginia due to the approaching of the Hurricane Florence, while millions of residents of the coastlines have been asked to leave their homes.
The category 4 hurricane is located about 575 miles (925 km) southeast of Cape Fear, North Carolina packing maximum sustained winds of 130 miles per hour (215 km per hour), it said. Tropical-storm force winds extend outward to 105 miles from the center.
"Rail cars with vehicles destined for export from Charleston have been diverted to secure holding areas until the storm passes", BMW spokesman Kenn Sparks said.
No tropical storm/hurricane watches or warnings are in effect for Barbados.
A hurricane warning is in effect for South Santee River, SC, north to Duck, NC, and the Albemarle and Pamlico Sounds.
It was the second such drop in the space of hours, but the Miami-based NHC stressed it remained "a life-threatening situation" due to the risks of storm surge around coastal areas. In Hurricane Sandy in 2012, storm surge-induced flooding measured as high as 9 feet above ground in parts of NY and New Jersey, leading to billions of dollars in damages.
The full impact of storm surge on the coast will depend on whether the storm's arrival coincides with high tide.
Storm surge, the massive mound of water that builds up and comes ashore during a hurricane, is often the deadliest and most destructive threat from the storms.
Helene, which has been downgraded from a hurricane, is among a glut of tropical storms brewing in the region, with mass evacuations under way in southern USA states as Hurricane Florence barrels across Virginia and the Carolinas. The storm is expected to slow down, stall and then perhaps wander just off the Carolina shore as it nears the coast Thursday, Friday and Saturday.
"As the system progresses westward into the eastern Caribbean Sea, more organized convection trailing Isaac is expected to affect Barbados, bringing moderate to heavy showers and occasional gusty winds from early Thursday morning and into Friday", the weather chief said. His remarks fell flat in Puerto Rico where islanders are continuing to struggle to recover a year after the Category 4 storm.
Two other tropical storms - Isaac and Olivia - have also been in the vicinity this week, with the National Weather Service estimating that some 10.15 million people lived in areas under either hurricane or tropical storm warnings.
A National Oceanic and Atmospheric Administration (NOAA) Hurricane Hunter aircraft is now en route to investigate the depression, according to the U.S. National Hurricane Center.
Subtropical Storm Joyce, which formed in the North Atlantic Tuesday, is also not expected to hit the U.S. It is forecast to become a tropical storm in the next day or so while drifting to the southwest. The NHC is encouraging officials in northeastern Mexico, Texas and Louisiana to monitor its progress.