Tropical Storm Ernesto gained strength overnight as it barreled toward Jamaica, while Florence, the sixth named storm of the season, formed in the eastern Atlantic Ocean on Saturday, US forecasters said.
At 0900 GMT, Ernesto was about 690 miles (1,110 kilometers) southeast of Kingston, moving westward at 18 miles per hour with top winds blowing at 60 miles per hour, according to the Miami-based National Hurricane Center.
The latest forecast says the storm would pass just south of the island as a category one hurricane on Monday, though the NHC urged Jamaicans to monitor Ernesto's progress.
Jamaica has issued a tropical storm watch for the island, meaning tropical storm conditions are possible in the coastal area within the next 48 hours.
But forecasters warned the storm is also headed for Honduras, Guatemala, Belize, Mexico's Yucatan Peninsula and Cuba as a hurricane between Tuesday and Thursday.
Further east, Florence had top winds of 40 miles per hour as it moved in a west-northwestward direction. It was located about 330 miles west of the southernmost Cape Verde Islands and was not expected to reach hurricane status.