I'm pretty sure I witnessed one of those. I was working at a store as mgr on call, the storm outside was blowing the carts around, so the stockman was outside trying to collect them. I went outside to tell him to stop and get back inside. I look to my left and the dirt from the HS baseball diamond suddenly blows outward in every direction. I look back to the stockman, a heavy set kid, and he's been knocked off his feet. Something catches my eye to the right and I turn to see one or two of those hard plastic kiddie wading pools go sailing off in the direction of I-88 (right next to the store). This all happened in a couple of seconds, so I went back in, got on the PA and asked everyone to go to the back of the store. The weather was coming from behind the store, so I couldn't tell if something worse was coming. I also didn't know what I had seen on the ball diamond - microburst? Tornado dropping down? I got the stockman back inside & I watched the front of the store, in case someone else was outside and needed to get in (I had locked the doors).
I ended up getting mildly chewed out, but in my defense a store my dad had managed had a storm where the wind was pushing 1970s land yachts around in the parking lot (cat 1 tornado nearby). Better to protect everyone and be wrong than to not do so and be wrong.