Advances in Supercell Storm Research

Supercells are the most severe and long-lasting type of highly organized convective storms, with the greatest potential for producing extreme weather events and causing significant disasters. This article provides a comprehensive overview and recent highlights of supercell research, including the unique structure, environmental characteristics, and the formation and maintenance mechanisms of the mesocyclone. Buoyancy instability is a necessary ingredient in the supercell’s environment, whereas dynamic factors such as vertical wind shear and low-level storm relative helicity are more sensitive parameters for distinguishing supercells from non-supercells. The near-storm environmental parameters derived from multi-sensor observations are expected to enhance high-resolution nowcasting of supercell storms. Different types of supercells, including those producing distinct hazardous weather, exhibit unique reflectivity morphology and dynamical/microphysical structures. For instance, tornadic supercells have a strong low-level mesocyclone, while severe hail supercells feature a strong and deep mesocyclone. Mesocyclones associated with damaging winds are accompanied by significant mid-level radial convergence, while those responsible for heavy precipitation are typically located at low levels. The vertical vorticity of mesocyclone is generated through the tilting of environmental horizontal vorticity by storm-related intense updrafts. The horizontal vorticity that tilts into the mid-level mesocyclone originates from the environmental vertical wind shear (where wind direction and speed vary with height), which produces the horizontal vorticity along the inflow to the storms. In contrast, the horizontal vorticity contributing to the low-level mesocyclone derives from two distinct mechanisms, i.e., environmental vertical shear in the boundary layer and gust front-induced baroclinicity. It remains unclear which mechanism is more dominant. Moreover, the maintenance and enhancement mechanisms of mesocyclones are complex and diverse in scenarios including mesocyclone embedding within heavy precipitation, storm mergers, and proximity to surface mesoscale boundaries (e.g., fronts, drylines, gust fronts, and their associated convergence lines). In recent years, based on super high-resolution numerical experiment results, the physical conceptual models of the supercell tornadogenesis have been updated. The newly revealed microphysical and dynamic characteristics from polarimetric Doppler radar observations enable more accurate hail size detection. However, the refined physical conceptual model of severe hail growth still requires improvement, and our understanding of the formation mechanisms of extreme wind gusts and flash floods associated with supercells remains limited.