Interactions between Supercells in Multistorm Simulations

Abstract Tornadic and nontornadic supercells have been observed in close proximity to one another, despite coexisting in a similar environment. One possibility is that localized heterogeneity in the environment produces changes in tornadogenesis likelihood. Such environmental heterogeneity may be induced by supercell thunderstorms themselves. This study investigates whether adjacent supercells influence one another, particularly focusing on influences to tornadogenesis likelihood. The study uses idealized numerical simulations of isolated supercells to identify how supercells introduce heterogeneity into their surrounding environment. Then, a series of multistorm simulations are used to investigate how storm-induced heterogeneity affects neighboring supercells and tornadogenesis likelihood. The most influential forms of storm-induced heterogeneity are found to be residual cold pools in the wake of supercells, dry air descending from aloft on the upshear flank of supercells, and left-moving splits from supercells. Residual cold pools and descending dry air weakened neighboring supercells and decreased the likelihood of tornadogenesis. Mergers with left-moving splits momentarily strengthened supercells and increased tornadogenesis likelihood before other storm-induced heterogeneity weakened these supercells. In the most hostile examples of storm-induced heterogeneity, neighboring supercells weakened to the point of dissipation. In the most favorable examples of storm-induced heterogeneity, low-level supercell updrafts nearly doubled their vertical velocity. These findings may explain why tornado production can vary between supercells coexisting in a similar environment. Significance Statement Supercells are intense thunderstorms that can produce tornadoes. While research has excelled in identifying environmental ingredients favorable for tornadoes, multiple supercells within the same general environment can vary in tornado production. This study investigates whether supercell thunderstorms themselves can influence neighboring storms and their likelihood of producing a tornado. It was found that supercells can modify the surrounding environment, creating regions where neighboring storms can have increased or decreased likelihood of producing a tornado. These results may be helpful for forecasting tornadoes during a multisupercell event.