Supercell Outbreak Evolving along a Cold Front in Coastal Southern China

The understanding of unusual supercell outbreaks remains limited. This study examines the development and environmental conditions of a supercell outbreak event 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 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 supercells developed their rotating updrafts upon encountering the 2–4-km scale misocyclones located at the convergent boundary of the cold front. The rotating storms were enhanced when they traversed the intersection zone created by the cold front and convergent boundaries under the influence of 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 clustered supercell outbreak. These findings may offer valuable insights on improving severe weather forecasts in this tornado-prone area.