A few days ago in North Dakota, storm chaser Mike Olbinski made this absolutely incredible time-lapse video of undulatus asperatus clouds. This class of cloud is the first cloud category added to the International Cloud Atlas since 1951. Olbinski writes:
We were chasing northeast of Bismarck, North Dakota and as storms were dying out, we decided to go for a lone cell on the backside of a line of storms. We knew it had a hail core on it and we were hoping that we might get some nice sunset color at least on the storm as it moved past us, and hopefully some lightning bolts. But we had no idea what we were about to encounter. The clouds were taking on a very different, curvy, wave-like appearance and suddenly we knew what we were seeing.
Undulatus asperatus clouds are a rare phenomenon and actually the newest named cloud type in over 60 years. I've seen tons of photos of them, but never anything like what we witnessed last night. We had a storm with hail in front of us and flashing lightning which was fantastic. But then we had this layer of undulatus clouds flowing across our view. Watching them was amazing already, but then the sun slowly appeared from behind some clouds to the west and lit up our storm like nothing we've ever seen before. We were like kids in a candy store. Running around, doing our best to capture it from every possible angle.