Thunderstorm activity become more concentrated two days later while located 60 mi ( 97 km ) south of Zinhuatnejo .
The NHC noted that the disturbance could become a tropical depression within hours .
Thunderstorm activity become more concentrated two days later while located 60 mi ( 97 km ) south of Zinhuatnejo , and the NHC noted that the disturbance could become a tropical depression within hours .