Abstract:By using ERA5 reanalysis data, and the surface automatic weather station, lightning locator, S-band dual-polarization radar and X-band phased array radar data, we analyze the ambient conditions and severe storm structure of the elevated thunderstorm that triggered localized hail in Zhejiang Province on 21 February 2024. The results show that the thunderstorm developed in front of the high-altitude southern trough and behind the surface cold front. The stratification configuration was “cold and wet-warm and wet-cold and dry” from bottom to top, and the low-level stratification was neutral and stable, so it was a typical elevated thunderstorm. During the process of thunderstorm activity, there were convective instability and symmetric instability in the middle layer, and the warm and wet air climbed along the cold air cushion, rapidly creating deep and strong vertical convection on the top of the inversion layer.The updraft center was in the middle troposphere behind the front. The storm moved on the side of the cold air, and the forward unstable area led to the continuous development of the storm. With the increasing height of the centroid and the strengthening updraft, the intracloud lightning above the 0℃ layer occurred much more frequently, causing the increase of solid hydrocondensate particles, which was conducive to the formation of hail. The dense area of intracloud lightning showed a good consistency with the hail falling area. The X-band phased array radar showed that the core of horizontal reflectivity factor of the hail cell was initially located above the 0℃ layer. The solid hydrocondensate particles in the core partially melt when passing through the warm and wet layer during their falling down, and then rapidly cooled down when through the cold cushion, partially frozen. In the end, they fell to the surface as rain mixed with hail.