Here are the 5 PM AST Key Messages on <a href="https://twitter.com/hashtag/Dorian?src=hash&ref_src=twsrc%5Etfw">#Dorian</a>, which is expected to intensify before reaching the Lesser Antilles late Monday into Tuesday. For more information see <a href="https://t.co/tW4KeFW0gB">https://t.co/tW4KeFW0gB</a> <a href="https://t.co/vU4h9gapfB">pic.twitter.com/vU4h9gapfB</a> —@NHC_Atlantic

Forecasters say the fourth tropical storm of the Atlantic hurricane season is maintaining its strength as it moves toward the Windward Islands.

The U.S. National Hurricane Center said Sunday that tropical storm Dorian could intensify to near hurricane strength over the eastern Caribbean Sea by Tuesday.

As of 8 p.m. ET on Sunday, Dorian's centre was located about 540 kilometres east-southeast of Barbados and was moving west at 23 km/h. Maximum sustained winds are at 85 km/h.

A tropical storm warning is in effect for Barbados, St. Lucia, St. Vincent and the Grenadines. A tropical storm watch was issued for Grenada and Martinique.

Forecasters say Puerto Rico, the Dominican Republic, Haiti and the Virgin Islands should monitor Dorian's progress.