An analysis on tornadoes in typhoon Ewiniar

Two tornadoes occurred in the spiral rain-band of typhoon Ewiniar (1804) on 8 June 2018. They struck Hengli town of Nansha district in Guangzhou city and Dali town of Nanhai district in Foshan city, respectively. Using various observation data, the synoptic environment and radar echoes for the tornadogenesis were analyzed. The results show that the tornado at Guangzhou was rated EF3 and located at the peripheral of typhoon Ewiniar in the northeast quadrant, while the tornado at Foshan was rated EF1 and developed in the inner region of Ewiniar to the east of its center. The synoptic environment for the above tornadoes show a typical circulation pattern with upper-level divergence, coupled with strong southeasterly jets at mid- and low-level over the Pearl River Estuary. The environmental conditions for the tornadogenesis include strong low-level vertical wind shear, high storm relative helicity, weak CAPE and CIN and low LCL. There were mesoscale convergence lines and small-scale vortices in the surface. Hook echoes, Fin echoes and moderate mesocyclones of tornado storms in low-level can be detected in observations of the CINRAD/SA radar. The tornadoes were located at the top of the hook echoes and near the center of mesocyclone. The features of mini supercell and tornadic debris signatures (TDS) were more obvious at Foshan CINRAD/XD radar observations than in observations of Guangzhou CINRAD/SA radar, which is deployed in Dali town of Nanhai district.