Significant Tornado Events Associated with Cell Mergers

Cell mergers have long been believed to play a role in tornado production, although the exact mechanisms are poorly understood. Several studies have noted the resultant thunderstorm intensification that occurs during a cell merger event (e.g., Cunning et al. 1982, Westcott and Kennedy 1989). Numerical simulations (e.g., Tao and Simpson 1989, Kogan and Shapiro 1996, Bluestein and Weisman 2000) have examined the role cell mergers play in the evolution of a storm, often noting an intensification of the primary storm following a cell merger. Several observational studies (e.g., Lee et al. 2006, Wurman et al. 2007, Rogers and Weiss 2008) have noted the relationship between cell mergers and tornado occurrence. Both Lee et al. (2006) and Rogers and Weiss (2008) found that approximately one-half of tornado reports were associated with cell mergers in separate case studies.