Satellite imagery and C-band radar on the R/V Mirai detected an isolated convective cloud band over the western tropical Pacific, and dropsondes observed the surrounding atmospheric environment. The reasonable development mechanism of this unusual cloud band is investigated using observational and numerical simulation data. Although theoretically, the surrounding atmospheric profile supported convective rolls, only a single cloud band was developed. Numerical simulations revealed a single cloud band and roll structure without condensate in the boundary layer. A westerly jet just above the cloud band influenced the environment with strong vertical shear supporting convective rolls; this was maintained by a typhoon at a distance of 1500 km away. A large-scale convergence in the meridional wind was also accompanied with this westerly jet. This special environment made by a typhoon could develop the unusual single cloud band.