Boris came from a tropical wave that moved off Africa on June 8. It passed near the Cape Verde Island with no convection. It went across Central America on June 23. The wave was very poorly defined on satellite images for many days. The first signs of a circulation on satellite imagery appeared on the 26th. It was about 250 miles south of the Gulf of Tehuantepec. The system became a tropical depression on the 27th when convective banding increased around the center.