At 5 p.m. Tuesday, the center of the tropical storm was located approximately 916 miles east-southeast of St. Croix near 14.6 degrees North, 51.3 west.
Isaac was moving west Wednesday afternoon at a speed of nearly 17 miles per hour.
The NHC forecast track shows the storm decreasing in forward speed as it heads west towards Central America. "A slow motion across portions of eastern SC is forecast Friday night through Saturday night".
Hurricane Helene is now churning northeast through the Atlantic Ocean around 655 miles (1,055 km) south-west of the Portuguese Azores with maximum sustained winds of 70mph. Little change in strength is expected over the next several hours.
The estimated minimum central pressure is 1000 mb (29.53 inches).
The "cone of error" in the forecast track only predicts where the storm's center might go, and even on its edges, winds can push a powerful storm surge into shore dozens of miles from where Florence's eyewall strikes land.
Florence is expected to produce heavy and excessive rainfall, NOAA noted.
Fox News reported that sustained winds were picking up a bit along the North Carolina coast. Earlier forecasts showed that the storm was slated to directly hit around North and SC.
According to the National Hurricane Center, the following warnings and watches are in effect.
As of Wednesday afternoon, the storm was not forecast to hit the Cayman Islands, but residents should continue to monitor its progress.
A yellow - "be aware" - warning, which also covers parts of South Ayrshire, was issued by the Met Office today.
The latest occurrences of the weather phenomenon, known in some areas as hurricanes, and elsewhere as cyclones or typhoons, bring huge danger to life, property and the local environment. This rainfall may cause life-threatening flash flooding. We're talking about hurricanes and storms, obviously. Persons located within these areas should take all necessary actions to protect life and property from rising water and the potential for other risky conditions.
The water could reach as high as 9 to 13 feet "from Cape Fear to Cape Lookout, including the Neuse, Pamlico, Pungo and Bay Rivers".
The mayor of a SC city in the path of powerful Hurricane Florence is warning citizens to get out or stay "at your own peril".