Environmental Controls on Tornadoes and Tornado Outbreaks

In this article, the global climatology of tornadoes and current understanding of the synoptic- and meso-scale environments of tornadoes and tornado outbreaks are reviewed. The study of tornadoes involves the investigation of atmospheric processes at global- to micro-scales and has advanced the understanding of multiscale processes. Global-scale circulation controls synoptic-scale processes such as extratropical cyclones, upper-level jets, and anticyclonic circulation; synoptic-scale processes affect mesoscale processes that cause severe thunderstorms and tornadoes. Studies of the near-storm environment of tornadoes and tornado outbreaks over decades have improved our understanding of differences in environmental parameters such as vertical shear and buoyancy between tornadic and nontornadic thunderstorms. Composite parameters associated with vertical shear and buoyancy have been developed and found to be skilful at predicting the potential of tornado occurrence. However, false alarm ratios for tornado prediction are still large. Since it is still a challenge to predict based on the environment whether or not a tornado will occur, further understanding of the near-storm environment of tornadoes and the development of new meteorological parameters to improve prediction skill are required in the future studies.