•Some tropical disturbances form in association with
mid-latitude troughs migrating
toward lower latitudes, some form from ITCZ-related convection, but most develop from easterly
waves.
•Easterly waves, or undulations in the trade wind pattern, spawn hurricanes in the Atlantic (typically 2–3000 km).
•Only about 10% tropical disturbances intensify into more
organized, rotating
storms.