A summary of radar and in situ near-ground observations within winter tornadic vortices during the Shonai Area Railroad Weather Project in Japan

Winter tornadic storms over the Japan Sea area have been observed during the Shonai Area Railroad Weather Project. In order to characterize vortices near the surface, we have installed 26 AWSs (WXT520; Vaisala) at intervals of 4 kilometers in the area around the Shonai plain. Each device was been mounted on the top of a steel pole as high as 5 meters. The observation intervals are 1 second for wind direction and wind speed, and 10 seconds for temperature, humidity and pressure. The PPI observations at low elevation angle from the X-band Doppler radar at 30-s intervals, as well as near-surface in situ measurements with high temporal resolutions provided unique dataset to analyze detailed tornado structures. Since the winter of 2007, over 20 cases of winter tornadic vortices were observed using the AWSs and the X-band Doppler radar. In this presentation, we will present properties of the surface winds and pressures and the radar reflectivity and velocity fields inside of core regions.