Abstract:In Taipusi Banner of Xilin Gol League, Inner Mongolia, a rarely-seen EF3 strong tornado occurred on 25 June 2021, resulting in 6 deaths and a large number of buildings’ damage and other losses. Based on meteorological observation data, automatic weather station data, CB-Doppler radar observation data of Zhangbei, Hebei Province, FY-4 satellite data and NCEF FNL (1°× 1°) 6 h reanalysis data, this paper comprehensively analyzes the process of the strong tornado. The results show that this tornado occurred in the background of unstable stratification environment of the forward-tilted trough. The strong conditional instability in the middle and low troposphere (the vertical temperature lapse rate at 850 hPa and 500 hPa was about 7.7 ℃·km-1), abundant water vapor in the lower layers, medium-strength convective available potential energy, and strong 0-6 km vertical wind shear provided favorable environmental conditions for supercell storms and tornadoes. In addition, the 0-1 km vertical wind shear was 8 m·s-1, and the lifting condensation height was 1.0 km, which provided relatively favorable environmental conditions for the occurrence of supercell storms and tornadoes. The convergence line accompanying the ground dry line triggered the parent storm that produced the tornado, and then evolved into the supercell. The radar reflectivity factor showed the characteristics of a typical hook echo, the inflow gap of warm and wet air at low level, the weak echo region at low level, the overhang echo at middle and high level, and the moderate-strength mesocyclone, etc. In the process of the formation and extinction of the tornado, three supercell storms formed successively, and all of them appeared in the isolated convective storm form. The tornado occurred at the top of one of the supercells, which was the junction of the front updraft and the rear downdraft. The possible start time and path of tornado based on the evolution of mesocyclone intensity analyzed by radar are in good agreement with the time of field investigation. Except for the strong tornado, this series of supercells also produced large hail and linear convection gale (thunderstorm gale), the strong echo center was significantly tilted from low to high, and the maximum reflectivity factor was as high as 65 dBz. In addition to the moderate-strength mesoclones, there was also obvious mid-level radial convergence in the diagram of radial velocity. At the time of supercell storm formation, the vertical integrated liquid water content (VIL) was as high as 73 kg·m-2, the VIL density was 4-5 g·m-3. These radar echo characteristics indicate the existence of large-sized hail, while the mid-level radial convergence was the radar echo characteristic of thunderstorm gale.