Preliminary analysis of a winter tornadic storm observed with radar and in situ instrumentation

Winter tornadic storms over the Japan Sea area have been observed during the Shonai Area Railroad Weather Project between 2007 and present. While the wind and reflectivity structures of tornadoes have been already extensively studied by remote sensing techniques, near-surface in situ measurements have to be performed primarily with surface-based instrumentations (e.g., anemometers). In order to characterize winter tornadic storms near the surface, we have installed 26 weather transmitters (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. In this presentation, we will introduce radar and in-situ measurement in winter tornadoes on December 5 2007. The distance between the radar and the 5.5-m-AGL in situ measurements (1-sec wind direction and wind speed / 10 sec temperature, humidity and pressure) was 1.9km. The in situ measurements were obtained core flow region of the tornado and the Doppler velocities were observed at 110m AGL. In addition to the radar and in-situ observations of tornado core, we will introduce radar high temporal observations (at 30-s interval) over the genesis region.