Fast scan radar observation of tornadic supercell in Tokyo during TOMACS

In 2010, a project Tokyo metropolitan area convection study (TOMACS) started. The aim of the project is to investigate extreme phenomena in metropolitan area, such as localized heavy rain, tornado, downburst, etc., and to clarify mechanisms of such phenomena. In this project, the authors installed a Ku-band "fast scan" radar (MRI-Ku) in Musashino-shi, Tokyo in 2011. On July 23, 2013, localized heavy rains occurred in Kanto area and the traffic in Tokyo was paralyzed by the storms. At 16JST (Japan Standard Time), a cell which had the characteristics of supercell, such as a hook echo, WER and a misocyclone(MC), generated a tornado in Chofu-shi, Tokyo and MRI-Ku successfully captured the supercell which was only 7.5km away from the radar. The radar observation by MRI-Ku revealed the followings : 1) At first, the hook echo and MC had generated at about 1km AGL and then they formed near the ground, 2) the tornado was generated on the flanking line about 2km away from MC, and 3) MC and DRC (Descending Reflectivity Core) may have affected the tornadogenesis.