Intensity and Structure Changes of Low-Level Tornadic Vortices during Landfall over the Japan Sea Area
From our observations so far, it is found that vortices often develop over the Japan Sea, intrude into land, and sometimes cause strong wind gusts. In such cases, the property of vortices over the sea is important for the gust detection system. However, if the property of vortices changes rapidly during landfall, the present detection and tracking system that relies on continuous change in vortex property may not work well. Thus, it is necessary for the system design to clarify the change in the properties of vortices during landfall.
In this presentation, we will discuss the intensity and structure changes of tornadic vortices during landfall. Detail analysis of the radar data with high temporal (at about 50-s interval of each volume-scan) and high resolution (analyzed vortices are within 3.5 km from the radar) at the low-level atmosphere (from 100 to 400 m) during landfall of vortices revealed some features as follows: (1) maximum tangential velocity decreases rapidly after landfall, (2) the decrease of tangential velocity can be seen to propagate upward from the lowermost level after landfall, (3) vortices tilt rearward with height before landfall.