Civil and Environmental Engineering Publications

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Geophysical Research Letters





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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.


Using a long-term data set (1875–2019), we investigate whether the month having peak tornado frequency changes over time in southern Ontario, Canada. Using only F/EF2+ tornadoes and 10-year rolling periods having modes at 5-year intervals, we find a statistically significant (99% confidence interval) moderate positive trend. However, we identify no statistically significant trend (positive or negative) using the same methods with tornado data from neighboring US states Michigan and New York. Though we do not investigate causes here, the study is the first to identify a robust long-term trend in the frequency of significant tornadoes for any region of Canada. Such a shift also has implications for public safety, with the occurrence of such tornadoes later in the year having the potential for greater impacts.

Citation of this paper:

Sills, D. M. L., Durfy, C. S., & de Souza, C. P. E. (2022). Are significant tornadoes occurring later in the year in southern Ontario? Geophysical Research Letters, 49, e2021GL096483.

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