Tornado Fatalities: An Environmental Perspective

Deadly tornadoes are rare events, but that level of rarity varies with many factors. In this work, we summarize and update past research on tornado fatalities, and also discuss the environments of deadly tornadoes both from the perspective of proximity soundings (i.e., point-based) and self-organizing maps (i.e., two-dimensional). In our study of 16 232 tornado events from 2003 to 2017, we find that deadly tornadoes are disproportionately likely to have high (E)F-scale ratings, to have right-moving supercell parent storm modes (deadly QLCS tornadoes are exceptionally rare and tend to result in only one death when they do occur), and to occur during the winter and spring. Warning skill is generally higher for deadly tornadoes than for nondeadly tornadoes: 87% of deadly tornadoes were warned in advance, and nearly 95% of tornado deaths occurred within an active warning. The same environments are warned well for both deadly and nondeadly tornadoes, but the deadly tornadoes tend to occur in environments that are less conducive to weaker (E)F0–1 tornadoes. We identify four prototypical deadly tornado scenarios using self-organizing maps, ranging from marginal environments resulting in relatively few fatalities to major deadly outbreak events. Overall results indicate that the most dangerous tornadoes (i.e., those with high numbers of deaths per deadly tornado) also generally occur in environments and under conditions in which warning skill is high. While, generally speaking, the correct storms are being warned, we include some recommendations for additional research and further improvement.