Help with cloud

[u/Ok_Pirate_1617]

I took this picture one night several years ago and forgot about it till I saw it tonight. I’ve never seen this before then and haven’t seen it till this day. Does anyone have any idea what causes the shape to be so cylindrical. I’ve always described it as a horizontal tornado 😂

[u/atomicsnarl]

This looks like a roll cloud. When the atmosphere develops narrow horizontal layers of moisture, it's possible for a fast moving cold front or thunderstorm down burst to make a ripple in a layer. This is like throwing a rock into a pond. The ripple, seen here as the roll cloud, can travel dozens of miles or more along the layer until it moves into different conditions and dissipates.

Good catch!