The low drifted westward, and interacted with Hurricane Klaus to its east.[1] Initially cold-core in nature, the system gradually built downward to the surface, and on October 9, the low developed a low-level circulation; at 1200 UTC the National Hurricane Center classified it as Tropical Depression Fifteen while located near the Cuban city of Caibarién,[2] though the cyclone was initially subtropical in character.[3] To its east, Tropical Storm Klaus continued to weaken; the depression absorbed most of Klaus and became the dominant system.[1] The storm tracked parallel to the coast of Cuba before veering northward and crossing the Florida Keys, where it intensified into Tropical Storm Marco about 35 mi (55 km) south-southeast of Key West, Florida.[2]