I just happened to be in Parker Colorado (near Denver) yesterday when the Tornadoes touched down. I was headed into a restaurant for dinner when we looked up and saw this. There were no sirens and at first the people around us didn’t notice.
I didn’t learn until later that it’s the most dangerous when it’s straight up and down.
I head conflicting reports of how close it actually was to where I was at. The odd thing I didn’t notice until it was over was how still it was. No wind. Despite living in both Iowa and Missouri, this is the first time I’ve seen a tornado. There were two tornados that touched down and luckily no one was hurt.