<p dir="ltr">Tornadoes have caused billions of dollars in damage and are one of the leading causes of
weather-related deaths in the United States each year. Recent studies have suggested spatial
shifts in tornado activity, though the reason is unclear. Extratropical cyclones (ETCs), which
are strongly associated with the jet stream, are known to produce an environment favorable
for tornadoes in their warm sector. However, little recent research has been done on the
spatiotemporal relationship between tornadoes and ETCs, so there is a poor understanding
of whether or not the changes in tornado activity are affected by ETC patterns. ERA5
reanalysis, ETC tracking, and historical tornado data from 1980-2022 are used to analyze
the climatology of tornadoes relative to ETCs. We found that 73% of F/EF1+ tornadoes
occurred within 2000km of an ETC and are likely associated with the ETC. Most of those
tornadoes occurred near the median position around 465km away from and to the southeast of
the ETC center. Of those tornadoes, 68% occurred in large outbreaks of 6 or more tornadoes,
where most tornadoes formed closer to and to the southeast of an ETC track as compared
to small outbreak and isolated tornadoes. The spatial and relative distributions were similar
across all intensity levels, though stronger tornadoes tended to have more tornadoes directly
to the southeast of an ETC. Seasonal variances in tornadoes strongly corresponded with
seasonal changes in the jet stream. Summer tornadoes occurred in northern portions of
the US when the jet stream shifts poleward. The jet stream and ETCs are also weakest
in the summer, and the weakest association was found in summer tornadoes based on their
distribution relative to ETCs being more uniform towards the northeast and north-southeast
directions. Winter tornadoes occurred in more southern portions of the US when the jet
stream shifts equatorward, and they had a stronger association with most of the tornadoes
occurring to the southeast and closer to the ETC center, aligning with a strong ETC and jet
stream in the winter. Finally, tornadoes and ETCs had strong spatial covariance and showed
similar linear trends, including a similar rate of change in the eastward shift, providing
strong evidence that a shift in ETCs may be driving the shift in tornadoes. Furthering our
understanding of the relationship between tornadoes and ETCs will help to better predict
how tornadoes will change in the future based on changes in ETCs.</p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/26348689 |
| Date | 22 July 2024 |
| Creators | Lauren Ann Kiefer (19192885) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/_i_Analyzing_the_Climatology_of_Tornadoes_i_i_Relative_to_Extratropical_Cyclones_i_/26348689 |
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