Canadian tornadoes, 1950–1979

Abstract

Abstract Other than the ground‐breaking work of McKay and Lowe (1960), little has been known about the incidence of tornadoes and the risk of tornado damage in Canada. Data concerning tornadoes during the period 1950 to 1979 (and earlier) have been gathered from many sources and processed to arrive at a set of quantitative conclusions concerning some of their physical characteristics and climatology. The data indicate that tornado incidence (the number of tornadoes per unit area per unit time) in populated sections of Canada is compatible with the incidence values published for adjacent American States, and that the highest annual probability of tornado damage is in southwestern Ontario (0.05 to 0.1%) followed by southeastern Manitoba (0.05%). In terms of size, the Canadian tornado (regardless of intensity) has median damage dimensions of 6 km in length, 80 m in width, and 1 km2 in area. In southwestern Ontario, the return period of a strong or violent tornado is 5 years, and it is likely to have median damage dimensions of 57 km in length, 790 m in width, and 78 km2 in area.