A hurricane warning remains in effect for Grand Cayman, as Tropical Storm Ian continues on its path through the Caribbean Sea.

As of 4am Sunday, it was 345 miles south-southeast of Grand Cayman, moving at 12 miles an hour, with maximum sustained winds of 50mph.

According to the US National Hurricane Center, the storm is forecast to continue moving westward before taking a turn northwestward later today, passing the Cayman Islands on Monday morning, and approaching western Cuba as a major hurricane on Monday night or early Tuesday.

The Cayman Islands National Weather Service, in its 4am update, said Grand Cayman can expect the onset of tropical storm-force winds from 4am Monday, and those will continue until 3pm Monday.

The closest point of approach is predicted to be 99 miles southwest of Grand Cayman at 8am Monday.

If the storm continues on its current path, Cayman forecasters say, the island may experience widespread thunderstorms from Sunday morning, with tropical storm conditions late into the night and possible hurricane conditions from early Monday morning as the system nears the Cayman Islands. Extremely rough seas accompanied by storm surge are also expected. Swell generated by Ian will spread into the Cayman area later Sunday.

The National Hurricane Center said the storm is expected to rapidly intensify later Sunday, and Ian is likely to be a major hurricane when it nears western Cuba in about 48 hours.

A flood warning will be in effect for the Cayman Islands, with rainfall of up to 4 inches expected on Monday.

Gusty winds are likely across all three islands from Sunday night. On Grand Cayman, winds of 20-30 miles per hours are expected on Sunday night, followed with winds of 45-55mph, with higher gusts, on Monday morning. On the Sister Islands, winds of 15-20mph, with higher gusts, are expected on Sunday and Monday.

A marine warning will be in effect for all three islands, and all marine craft are advised to seek and remain in safe harbour. Estimated wave heights of 6-8 feet are expected Sunday, rising to 10-13 feet, especially along the south coast on Monday. Swells of 5 to 7 feet are likely, along with 1 to 3 feet of storm surge, forecasters said.