Tornado Losses in the United States

Insurance data for tornado damages during 1949-2006 revealed 793 tornado events that each caused >$1 million in losses. The average annual loss of these tornado catastrophes is $982 million, an amount that greatly exceeds the existing average of $462 million based on estimates from government records. Tornado losses typically occurred in only one state but when tornadoes occurred with floods or hurricanes, the losses occurred in four or five states. Tornado catastrophes and losses were most frequent in Texas, Oklahoma, and Kansas, and relatively frequent in many Midwestern states. The temporal distribution of tornado catastrophes revealed large interannual variability with a few years of major loss and many years with none. Tornado-only catastrophes and their losses had flat trends for 1949-2006 but trends were upward for cases of tornadoes with floods and cases when tornadoes occurred with hurricanes. These result from upward trends in flooding across the nation and the tornado-hurricane temporal increase results from time-related increases in hurricane-prone storm conditions and from coastal society's growing vulnerability to storm damages.