Tropical storm Ernesto strengthened Monday as it headed for a brush with the Caribbean coast of Honduras and Nicaragua on a track that might carry it to the Belize-Mexico border as a hurricane.

Nicaragua began evacuating hundreds of people from imperiled coastal fishing villages and Honduran officials said they were watching the storm closely.

The U.S. National Hurricane Center in Miami said the storm strengthened as it slowed passing Jamaica and had maximum sustained winds of 100 km/h Monday afternoon, up from winds of 85 km/h as it charged across the Caribbean in recent days.

It said the storm could grow into a hurricane during the night while dumping torrential rains on northern Honduras, including the Bay Islands that are popular resort areas for foreigners.

It said the storm could hit somewhere in Belize or along Mexico's southern Yucatan coast as a strong Category 1 storm on Wednesday. Ernesto hasn't made any direct hits on land since entering the Caribbean early Saturday.

The Hurricane Center said Ernesto was centred about 260 kilometres east-northeast of Cabo Gracias a Dios on the Nicaragua-Honduras border Monday afternoon and it was moving to the west-northwest at 19 km/h. It had been racing along at nearly twice that pace over the weekend.

Far out in the Atlantic, former Tropical storm Florence weakened into a remnant low.