Tropical Storm Humberto is forecast to become a major hurricane this weekend and a second system — likely to become Imelda — is a possible threat to Florida or other parts of the U.S. coast.

A fast-moving Hurricane Gabrielle was expected to bring heavy rain, high winds and a storm surge to the Azores islands starting Thursday night and into early Friday, forecasters said. A hurricane warning was in effect for the all of the islands in the volcanic archipelago,

At 5 p.m. Wednesday, the National Hurricane Center issued an advisory for the tropical storm. Tropical Storm Humberto is in the Atlantic Ocean, 550 miles east-northeast of the Northern Leeward Islands. The system is moving to the west-northwest at 15 mph, with maximum sustained winds of 40 mph.