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Missouri is having one of its most active tornado seasons on record — what’s behind the numbers?

A house and trees show damage from an EF1 tornado that moved through south St. Louis County on May 26 in this National Weather Service photo taken May 27, 2024. The National Weather Service surveys damage from tornadoes after they hit to determine the tornado's official rating.
Illustration by Theo Welling
St. Louis Public Radio / National Weather Service
A house and trees show damage from an EF1 tornado that moved through south St. Louis County on Sunday in this National Weather Service photo taken on Monday. The National Weather Service surveys damage from tornadoes after they hit to determine the tornado's official rating.

Missouri is having one of its most active tornado seasons on record. That’s also true in other places across the country, where tornado reports are running above average this year.

By Wednesday, Missouri had recorded the third-most tornado warnings since records became available in the 1980s, said Missouri State Climatologist Zack Leasor. With 184 warnings, Missouri is also ranked third nationally for the most 2024 tornadoes, after Texas, with 216, and Oklahoma, with 195.

An active tornado season means meteorologists at the National Weather Service are busy issuing tornado warnings and surveying damage from storms. Ben Herzog, science and operations manager at the National Weather Service in St. Louis, spoke with St. Louis Public Radio’s Kate Grumke about how tornado warnings have changed and what we know about climate change and tornadoes. This conversation has been edited for length and clarity.


Ben Herzog: The tool we use primarily to look for tornadoes is our radar, and one big limitation to that is it can't see what's happening on the ground. It sends these very brief pulses of energy into the atmosphere, and they can range from, if you're really close to the radar, a couple hundred feet off the ground, to the further you get away, they can be thousands of feet off the ground. And there's a lot that happens in the low levels of the storm there. So we rely on going out and surveying what actually happened on the ground.

Kate Grumke: What are the limitations to that? I think of the saying, ‘if a tree falls in the forest, and no one's around to hear it…’ What's the tornado version of that?

Herzog: A tornado has to hit something, and it has to hit something well-built for us to be able to rate it pretty highly. We see that with a lot of the higher-end tornadoes that are around. I think that's something they're dealing with with the Greenfield, Iowa, tornado. We actually have radar measurements that got really low to the ground, but not on the ground, that said it was a very strong tornado, perhaps an EF5, but it just didn't hit anything that was well-constructed enough to be able to classify it as an EF5. So that's a pretty big limitation. And then there'll be a lot of tornadoes, especially as you get out into the plains, where they're just going through fields and they don't hit anything at all. In fact, we had one of those, oh, probably a month or two ago in central Illinois. It was a day we had, like, nine tornadoes. I suspect that was the strongest tornado that we saw, but it didn't hit a thing. We drove around all those fields and tried to find it and couldn't find anything. So we had to actually rate that tornado EFU, which stands for "unknown," Enhanced Fujita Scale Unknown.

Grumke: It seems like we've been having a lot of storms lately with multiple tornadoes in them. Growing up here as a kid, I don't really remember that type of storm. So am I imagining that or did something change?

Herzog: I don't think anything in the environment necessarily changed. I think we're by and large seeing the same types of storms that we've seen for the last at least 100 years or so. But I do think there are a couple of things that are going on here. First of all, we went through a pretty significant upgrade to our radar about 10 years ago. That's when we went from what's called Single Polarization Radar to Dual Polarization Radar. With the advent of that Dual-Pol Technology, we're getting a lot more radar confirmation of actual tornadoes happening. So that's making it seem like there are a lot more tornadoes. The other thing, and this is, I would say, more of a hypothesis, but I think the proliferation of smartphones and people just having a camera in their pocket at all times makes it a lot easier for people to document those tornadoes, get those pictures to us. And well, if we see a picture of a tornado, we kind of have to call it a tornado. While some of the records may look like the number of tornadoes are increasing, especially if you go back to like the early 1900s or so, in actuality, it's just that we're getting a lot more reports of those tornadoes.

Grumke: And so with that in mind, what do we know about climate change and tornadoes?

Herzog: It's really difficult to associate climate change with, especially, individual tornadoes. And because the records for tornadoes are relatively inconsistent, and there are some data quality issues in there, it's really difficult to make direct comparisons between the changing climate and tornadoes themselves. What we do know, though, is that climate change is causing the conditions that are favorable for tornadoes to kind of come around more often. Not necessarily just tornadoes, either, just severe storms in general. We're seeing these very warm and kind of moist environments come together that are really necessary to get those severe thunderstorms to occur. There's also been some work that has shown us that tornado outbreaks are becoming more frequent. And so those are days where you're seeing a lot of tornadoes all at once. There's another study out there that shows tornado power in general has increased. And there's also some information that's showing us that tornado activity is actually increasing in the fall. So there is some kind of emerging science that does kind of relate climate change to tornadoes in general but again, to tie it to individual storms is pretty difficult.

Kate Grumke covers the environment, climate and agriculture for St. Louis Public Radio and Harvest Public Media.