 It does happen, and it is rare enough that the screaming that you heard, I have to admit, I did the same thing last year when I ended up in a similar situation. I think most storm chasers get extremely excited if they see two on the ground at the same time because it is rather rare. That's great. So the National Weather Service confirmed that there were at least 11 tornadoes during Monday night storms in the Chicago area. How do groups of multiple tornadoes come about like this?