The Tornado Climatology of 2011

[Randy Zipser]

I have been reading the ST thread about the Joplin tornado and it got me thinking about why 2011 was such a prolific and deadly year for tornadoes across the United States. According to the Storm Prediction Center, 2011 logged 2,240 NWS Local Storm Reports (LSRs), which is about 61% above the 14-year (2010-2024) mean of 1,392 LSRs. To this day, 2011 remains the single most active year in terms of reported tornadoes. But what factors have contributed to that particular year being the lone standout?

The following articles discuss the climatological factors related to 2011:

2011 Tornado Season Climate Factors: NOAA Physical Sciences Laboratory

https://www.npr.org/2011/05/25/136657481/whats-behind-2011s-deadly-tornado-season

 

[Mike Smith]

Thanks for posting, Randy. I've often wondered what made 2011 so extraordinary but I don't find the PSL discussion particularly convincing.

There is a tendency, it seems, to want to tie events to the tropics which may have no connection. That may be why NWS 30 and, especially, 90-day forecasts are so bad.

 

[Randy Zipser]

There is a tendency, it seems, to want to tie events to the tropics which may have no connection

I also noticed that "connection," Mike.

Each tornado season is unique because whatever atmospheric/oceanic factors that contribute in the late winter/spring months differ from year-to-year. So whatever came together in the spring of 2011 never came together in quite the same way before 2011 and also has never repeated since. It may never happen again, or that record could be surpassed next season, who knows? At least Harold Brooks back in 2011 left that question open, rather than rushing to some explanation or conclusion (which was the right thing to do as an objective researcher).

For now, it seems that random, natural variability is best answer we can come up with...