Numerical simulation of low-level misocyclones associated with winter convective cells: a case study from the Shonai area railroad weather project

This study describes the numerically simulated structure of low-level misocyclones associated with winter convective cells observed at 11 December 2008 during the Shonai area railroad weather project (Shonai area is located in the coast of the Sea of Japan, ~39N). In this case, convective cells were initiated along the cold front over the sea and misocyclones were embedded in the surface convergence line. Misocyclones were distributed at 2-4 km intervals and some of them landed.

The nonhydrostatic numerical model, JMA-NHM, is used to simulate the misocyclones. The model is initialized by MANAL, which data is an objective analysis made by JMA and horizontal resolution is 10 km, and no special observed data is assimilated in this case. The finest horizontal grid spacing is 250 m. The model succeeds in simulating convective cells and misocyclones along the surface convergence line. The simulated misocyclone is initiated below the height of 500 m, where the horizontal convergence is significantly strong. Then the misocyclone extends upward and reaches the height of 2 km. The structure of the misocyclone changes in the vicinity of the landfall. After the landfall, the vertical structure of the misocyclone greatly tilts to the advected direction. Until the conference, the results of higher resolution (~50 m in horizontal) simulation would be organized.