Cyclonic misovortices with a horizontal scale of 0.4 -1.9 km embedded within a convective snowband were observed by two X-band Doppler radars in the Japan Sea coastal region on December 31, 2007, during a cold-air outbreak. All vortices initially developed offshore, subsequently making a landfall. The structure and temporal evolution of these vortices during the landfall were investigated using high-resolution data obtained from two X-band Doppler radars.The studied vortices developed along a low-level convergence line characterized by cyclonic horizontal shear, suggesting that horizontal shearing instability was responsible for the initial development of the vortices. A detailed investigation was performed on a vortex that passed within a close range (< 10 km) of both radars and almost directly over two surface observation stations. As this vortex approached the coast, it extended upward with time and eventually reached a height greater than half of the echo-top height of the parent snowband. During the landfall, the vortex core diameter contracted markedly and its peak tangential velocity and vertical vorticity increased at lower altitudes. Such a temporal change of low-level vortex was associated with an intensification of low-level convergence around the vortex and the convergence line. These facts suggest that the stretching of the low-level vortex was responsible for the low-level vortex contraction and increase in peak tangential velocity and vertical vorticity during the landfall.

A wind gust of F0 scale occurred in Shonai town, Yamagata Prefecture, Japan, on 4 December 2015. It damaged some houses in a narrow valley 24 km from the coast of the Japan Sea. Around that time, one of many isolated convective clouds greater than 6 km in height traveled over the area. Observation of two Doppler radars with high resolution in time and space showed that a cyclonic vortex generated at the south edge of the convective cloud after landfall from the Japan Sea rapidly developed with increasing vorticity as it moved inland. The vortex traveled across a mountain, and its southern part near its center subsequently passed over the damaged area. The radius and vorticity of the vortex were 0.64 km (misoscale) and 0.048 s −1 , respectively. A hook-shaped echo, a vault-shaped echo, and a couplet of maximum and minimum Doppler velocities, which indicate the existence of a vertically oriented vortex tube, are clearly shown. This study discusses the development of the winter misocyclone observed by the radars in terms of the relationship with the behavior of the parent cloud and the possible topographical influence of the mountain and valley on the vortex structure.(Citation: Onomura, S., K. Kusunoki, K. Arai, H. Y. Inoue, N. Ishitsu, and C. Fujiwara, 2017: Rapid intensification of a winter misocyclone under an isolated convective cloud after landfall. SOLA, 13, 74−78,