2015 Volume 11 Pages 18-22
Cloud-to-ground (CG) and total (both CG and intracloud) lightning trends were investigated in a tornado-producing (F2) supercell thunderstorm that occurred over the Kanto Plain in Japan on 2 September 2013. The spatiotemporal signatures of mesocyclone (MC) and storm development were also analyzed using Doppler radar data. The results revealed that rapid increases of lightning flash rates (“lightning jumps”) occurred in CG and total flash rates 0-7 and 0-14 min before tornadogenesis, respectively, which are similar to those observed in the United States. However, the CG polarity change reported in previous studies was not observed, i.e., 96% of CG flashes were negative. The vertical vorticity of the MC was larger in the mid-level (4-6 km) than the low level (2 km) at the beginning stage of the lightning jumps, which might have led to updraft enhancement above the freezing level appropriate for the rapid increases in lightning flash rates.
