State of emergency declared in North and South Carolina as Tropical Storm Florence tipped to become hurricane

Tropical Storm Florence is becoming a "better organised" weather system that will likely strengthen into a hurricane late today, weather forecasters are warning.

The National Hurricane Center said today the storm was expected to become a "major hurricane" by Tuesday as it passes between Bermuda and the Bahamas on Tuesday and Wednesday. The storm is expected to approach the southeast US Coast on Thursday.

Officials in North Carolina were already bracing for impact, with North Carolina Governor Roy Cooper declaring a state of emergency.

He also urged residents to use the weekend to prepare for the possibility of a natural disaster.

"We are entering the peak of hurricane season and we know well the unpredictability and power of these storms," Gov Cooper said.

In South Carolina, Governor Henry McMaster also declared a state of emergency.

Gov McMaster emphasised that there's no way to know yet when and where the storm will hit land, or when evacuations might be called.

The US Navy is making preparations this weekend for its ships in the Hampton Roads area to leave port as Tropical Storm Florence approaches the East Coast.

The US Fleet Forces Command said in a news release that the ships will get ready in anticipation of getting under way Monday to avoid storm damage.

Admiral Christopher Grady said in a statement that the decision was based on Florence's current track, which indicates the area could see strong sustained winds and storm surges.

The National Hurricane Center said that Florence will start to rapidly intensify tomorrow, and be a major hurricane by Tuesday.

The news release notes that plans could change if forecasts indicate a decrease in the strength or change in the track of the storm.