Bands of rain spread across the Cape Verde islands as Tropical Storm Humberto moved toward the island group, weather forecasters said. A tropical storm warning was in effect for the southern Cape Verde islands of Maio, Santiago, Fogo and Brava, the National Hurricane Center in Miami said in its 8 a.m. EDT advisory. The islands are in the Atlantic west of Africa. Humberto, with maximum sustained winds of 40 mph, was about 105 miles south of the Cape Verde island of Praia, moving west at 12 mph, the center said. Humberto is forecast to strengthen during the next 48 hours and could become a hurricane on Wednesday, the hurricane center said. The storm was expected to maintain its course through Monday before shifting toward the west-northwest Tuesday. On its forecast track, Humberto\'s center was to pass south off the southern islands by Monday evening and move west of the islands Tuesday. Humberto was expected to produce 3-6 inches of rain across the southern islands, with up to 8 inches possible in isolated areas, the hurricane center said. The rains could produce heavy flooding and mudslides.