Abstract: On June 25, 2020, the Xiqing District of Tianjin, China, was affected by a convective storm accompanied by a mesovortex (MV), which has been producing record-breaking gusts (the gust speed reached 41.4 m s⁻¹) since 1957. To improve the scientific understanding of extreme thunderstorm winds due to such mesoscale vortex, the thermodynamic structure characteristics and maintenance mechanism of MV were analyzed using the Variational Doppler Radar Analysis System technique on radar data combined with multisource observation data. The results indicate that MV was initially born at a height of 2.0 km, and the contracting and stretching vertical vortex rapidly descended to the surface from this height, with the rotation speed increasing and the vortex diameter contracting. During this process, i.e., the surface transition from warm and dry to cold and wet cyclonic vortex, extremely strong winds appeared in the western overlap area of the MV and rear inflow jet (RIJ). MV evolution was closely related to the different properties in convective storms. In the mature stage of the MV, vertical circulation was formed through tilt updraft (TUD), RIJ, front flank downdraft, and forward low-level inflow. The rainwater evaporated and absorbed heat during the strengthening and descent of MV, leading to a considerable enhancement in the RIJ intensity and its continuous downward extension. The configuration of the cold pool and vertical wind shear plays a vital role in MV evolution—from the formation to development stages, the cold pool and low-level vertical wind shear from a height of 0–3 km reached equilibrium; from the development to mature stages, the cold pool and bulk vertical wind shear from a height of 0–6 km reached a balanced stage; and from the mature to dissipation stages, the intensity of the cold pool exceeded the bulk vertical wind shear, which is unfavorable for storm development. Distinct from the ground-reaching RIJ associated with typical bow echo, the RIJ in this event did not reach the ground but was instead coupled with the vertical downdraft of MV near an altitude of 1 km, further generating a vertically downward perturbation pressure gradient force. Meanwhile, the drag effect of rainwater facilitated the strengthening of the downdraft. During its descent, evaporation and heat absorption weakened the cold pool, which then intensified the surface wind speed, collectively leading to the extreme gale.