Tropical waves, also called easterly waves, are areas of thunderstorms and cloudiness that move off the west coast of Africa during the spring, summer, and fall. Tropical waves are usually carried in a westward direction by the easterly winds found along the latitudes near the equator. They are elongated, north to south oriented areas of relatively low air pressure. In the northern Atlantic Ocean during the summer and fall, tropical waves often form into tropical cyclones, especially during August and September.