It is aimed to analyze under what conditions thermals generated by the heat and shape effect of the city break through the atmospheric boundary layer. I used the urban meteorological Large Eddy Simulation model and the thermals over Kobe City are our targets. As a result, three factors were confirmed on the thermals which break through the atmosphere boundary layer. One factor is strong thermal buoyancy, and second factor is elimination of the stabilizing layer by another thermal and last factor is vapor amount. In addition, we could confirm the assembly of vortex. The assembly occur by vertical shear of horizontal wind. It is possible that the assembly strengthen each vortex. At last, I analyzed which factor is important for generating cumulus cloud.