In the Izu Oshima case, the turbulence closure model greatly influenced to the position of the front and associated rain band. In the experiments with DD, the front was simulated at the similar position to observation, while in the experiments with MYNN the front was shifted to the northwest of the island. The models with DD tended to simulate the more intense downdraft in the lee of the front than the models with MYNN. The back-building formations were seen in the experiments with DD, but the finer grid spacing models showed more distinct vertical flows along the front and associated cold pools. These differences in the vertical motions and the cold pool formations affected the position of the rain band. In Hiroshima case, the grid spacings influences to the position of the rain band.
Sensitivity experiments on the domain size and lateral boundary conditions showed the importance to have large domain and include of cloud microphysical quantities in the lateral boundary condition in Izu Ohshima case. However, the domain size and the lateral boundary conditions were little impact on the Hiroshima case.
In both cases, the 250-m grid model with the finest terrain representation showed the best performance in all experiments. These results demonstrate that the very high resolution NWP model with the large domain has the ability to better predict the meso scale rain band and associated precipitation.