, i say gustnado, rick.ole thing off. >> reporter: obviously this is a serious situation, but we do call it gustnado. it is a slang term, it's not in our glosserie our bible of terms. one meteorologist looks at that video and sees sort of a swirling around motion as the stage is about to collapse, and some flags changing direction, and that kind of leads him to believe that it was a gustnado. now what is a gust? tkpwr*uis a gustnado? it's a low cloud that is around the cold front. it typically is short-lived, it typically lasts a few seconds to a few minutes. it's not a tornado. even though it's called a gustnado. some folks might be saying it's just like a tornado, it's not. the cloud remains near the surface and rarely comes in contact with the thunderstorm above it. so it actually forms ahead of the thunderstorm, that's the main difference. if you see a dust devil, very similar to that, folks across the great plains and the midwest and arizona you are familiar with the term gustnado, or a dust devil. that

what is a gustnado? >> reporter: the definition is a low level rotating cloud that forms along the gust front or outflow of a thunderstorm, or the cold front. there is the video there, megyn. i guess a couple of meteorologists, you can see that swirl in the video, they are looking at that rotating swirl whipping around the dust and maybe some flags before the stage collapsed, and their thinking is yeah it could be this phenomenon called a gustnado, which is a vortex that forms along the front of a thunderstorm. i have to mention as well that some of the nooah meteorologists are disputing this. they think it was just a severe thunderstorm, straight-line winds that caused the collapse of the stage. i don't really know if we're going to find out what indeed caused the stage collapse. i guess we can all agree that it was weather related. a gustnado is a typically short-lived, lasts a few seconds to a few minutes, it's not a tornado even though it's called a gustnado. they might think the is related to a torn

a gustnado, not the same. a gustnado, actually is part of what we call this gust front. we know the gust front was to blame for this. the rain came down, the rain hit with air to the ground and then it pushed out. it was the wind pushing out ten miles ahead of the storm itself. here. but in front of this, where the wind is, you can get little spins, little eddies, little small, almost like dust-ups. if you think about an ice skater in the olympics, one foot on the ground, one foot here, bringing the arms in and that skater can spin pretty fast, that's a little bit of energy, momentum that you can get wind spinning faster than just this straight-line wind. let's go to this video. it's here. i'm going to show you what i see. >> some things look like it's twirling. >> there's something here. this dust is here. it's moving away. that doesn't mean it was there because the dust continues to come in from this direction. what i believe may have been more of the cause and this could cause a spin too. was that we have almost this wind tunnel effect which where this is where the gr

but violent wind gusts, something they called gustnados, swept up from the ground.f wind that swirl like a tornado in advance of a storm front too quickly to be detected. that is what apparently happened here. the wind gusts here were so isolated they never hit this part of the park, where kids riding the ferris wheel were unscathed. only a few hundred feet away om the concert stage. but 15 miles away at another outdoor concert, officials did order a mandatory evacuation. just 30 minutes before the state fair tragedy. the wind gusts moved so quickly here, it was impossible for some to e eape. but with severe weather in the air, experts say it's smart to have a plan and know a safe structure where you can take shelter. chris bury, abc news, indianapolis. >> such a sad story. those questions aren't going to be answered any time soon. there's so much confusion about who was supposed to be doing safety inspections. there was some talk about it, then they retracted it. it's got to be hard for those poor victims' families. >> the city doesn't seem to be responsible becaus