Shelf cloud video goes viral in Mississippi

A video of a shelf cloud over Mississippi has gone viral on social media.

A shelf cloud, or Arcus cloud, is a low-hanging horizontal cloud that forms along the leading edge of a thunderstorm.

Shelf clouds form when a thunderstorm pushes cold, dense air outward, colliding with warm, humid air and forcing it upward.

The cloud signals an approaching thunderstorm and is often followed by strong winds, heavy rain, and lightning.

The motion seen in shelf clouds is caused by strong winds, not rotation like a tornado.