Weather forecasters are keeping a close eye on Tropical Storm Helene, which formed just off the coast of West Africa and became a named storm at the United States National Hurricane Center on Saturday.
On Sunday, the storm was located about 125 kilometers southwest of Cabo Verde at 5 p.m. local time in Praia, with outer bands rain affecting the southern islands.
Helene has maximum sustained wind speeds of 100 kilometers per hour, and is moving west at 20 kph before an expected curve to the northwest. The storm is bigger than originally thought, and tropical storm force winds now extend 130 kilometers from the center.
Helene is forecast to strengthen as it passes near the Cabo Verde islands on Sunday. The NHC has issued tropical storm warnings for the islands of Santiago, Fogo, and Brava, all in the southern leeward group of the islands. Rainfall of 50-100mm is expected, with the possibility of 150mm in isolated locations.
Some rain may be welcome in Cabo Verde, where officials say the drought is the worst in 40 years with Brava among the hard-hit islands. Authorities reported the Poilão dam reservoir on Santiago dried up in June, although some rain reached Cabo Verde from a tropical depression in late August. Yet excessive rainfall heightens the risk of flash flooding and landslides, especially in mountainous terrain on the volcanic islands such as Fogo.
Helene is likely to become a hurricane on Sunday while still near Cabo Verde, and hurricane conditions are possible later in the day, the NHC said. A hurricane watch remains in effect.
Tropical Storm Helene formed unusually far east in the Atlantic Ocean, where tropical waves coming from West Africa typically take more time and distance across the ocean to intensify.
Helene follows in the footsteps of Fred, which in 2015 rapidly became a hurricane just off the coast of Senegal and, according to records dating to 1851, caused the first hurricane warnings ever issued in Cabo Verde. Fred formed as a tropical storm at 18.9W, according to U.S. meteorologists; Helene became a named storm at 18.5W.