Supercell Outbreak Evolving along a Cold Front in Coastal Southern China

Understanding of unusual cascaded supercell outbreak remains limited. This study examines the development and environmental conditions of a supercell outbreak that occurred on 26 March 2022, when 19 supercells formed within just 6 h in the coastal region of southern China. The focus is on analyzing radar characteristics and highlighting the role of mesocyclones along a surface cold front in driving the development of rotating storms. The cold front created significant variations in low-level vertical wind shear and conditional instability on its warm and cool sides. Most of the 19 supercells formed along the front or on its adjacent cool side. Both observations and simulations reveal that favorable dynamic conditions for supercell development appeared and concentrated in a relatively narrow area on the cool side of the front, influenced by directional wind shear near the surface, which drove the formation and positioning of supercells. Numerical simulations demonstrate that the supercell storms developed their rotating updrafts upon encountering the mesocyclone located at the convergent boundary of the cold front. The rotating storms was enhanced when they traversed the intersection zone created by the cold front and convergent boundaries and affected by the unique land–sea contrast of the Pearl River Delta. In sum, appropriate dynamic allocation of wind shear, cold front, and landform has facilitated development of the 19 cascaded supercells. The findings of this study may offer valuable insights on improving severe weather forecasts in this tornado-prone area.