 By early on October 6 , a low pressure area and circulation persisted over eastern Cuba in the middle levels of the atmosphere . The low drifted westward , and interacted with Hurricane Klaus to its east . 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 , though the cyclone was initially subtropical in character . To its east , Tropical Storm Klaus continued to weaken ; the depression absorbed most of Klaus and became the dominant system . 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 . 
