Tropical Storm Erika formed overnight in the Atlantic Ocean, the National Hurricane Center said. As of 8 a.m. ET, the storm had winds of 45 mph and was located 750 miles east of the Caribbean’s Leeward Islands. It’s moving to the west at 20 mph. Tropical storm watches have been posted for several islands in the Caribbean, including Montserrat, Antigua, Barbuda, and St. Kitts and Nevis. A tropical storm watch means that tropical storm conditions are possible within the watch area, generally within 48 hours, the hurricane center said.