On the Absence of Population Bias in the Tornado Climatology of Southwestern Ontario

Abstract

Rural population densities and tornado incidence (confirmed and probable categories) are compared for noncoastal regions in the southwestern Ontario peninsula. No apparent relationship is found between rural population density and F0–F4 categories as indicated by a linear correlation coefficient of −0.11. The statistical breakdown for F0–F2 groupings and F3 and F4 groupings of confirmed and probable categories, respectively, when linearly regressed against rural population densities produced correlation coefficients of −0.22 and +0.33, respectively;neither of which is statistically significant (5% confidence level). It is concluded that no apparent relationship exists between rural population density and tornado incidence for the confirmed and probable categories. However, regression analysis of rural population density versus F0–F2 events classified as possible tornadoes produced a correlation coefficient of +0.47 (significant at the 5% confidence level but not the 1% level). Since the possible category may be dominated by nontornadic events, a relationship between population density and severe nontornadic weather is possible. Some evidence is presented that lake effects may extend far enough inland to cause some of the apparent anomalies noted in the spatial distribution of tornadoes in southwestern Ontario. Other factors are noted that may account, in part, for the results obtained.