Analysis of a tornado event induced by landing typhoon "Rumbia"

In order to research the characteristics of the tornado process caused by the landing typhoon, and improve the ability of monitoring, potential forecasting and early warning, the on-site disaster survey data, the observation data of the ground-encrypted automatic station, the European reanalysis data (ERA5), Bengbu Doppler weather radar and Fuyang S-band dual-polarization radar detection data were used, to analyze the meteorological elements, atmospheric circulation, key physical factors and radar echo characteristics when the tornado happened on 18 August 2018. The results show that the tornado located in the northeast quadrant area of the " Rumbia " center, is accompanied by steep rising and falling air pressure, sharp drop in temperature, strong winds and short-term heavy precipitation, and the intensity is EF0. The area has the best collocation of convective effective potential energy (CAPE) and the storm horizontal relative helicity (SRH), the maximal 0-1km SRH is 149 m²·s^-2. During the period of increasing vertical helicity, Lingbi tornado occurred. Both radars can detect the hook echo of the supercell, with a central reflectivity of about 60 dBz, and there are bounded weak echoes and echo overhangs. The shape of the mesocyclone changed from an ellipse to a circle. At the same time, the low-level radial velocity difference of the TVS rapidly increased, and a tornado disaster occurred in Lingbi. In addition, the dual-polarization radar can detect the hook echo of the supercell at 165 km, which has a wider detection range of tornadoes, and can identify more obvious positive and negative velocity pairs and tornado debris signatures (TDS), having stronger detection ability to tornado.