Horseshoe cloud

A horseshoe cloud is a relatively uncommon meteorological phenomenon[1] which manifests as a cloud in the shape of a horseshoe or inverted letter "U".

[1][2] They occur when a horseshoe vortex deforms a cumulus cloud.

[2] The clouds are relatively short-lived[2] and is the last stage before one dissipates.

[3] Horseshoe vortex clouds are a form of "fair-weather" funnel cloud and are similar to the shear funnel type of funnel cloud.

[citation needed] A March 2018 instance was explained by the United States National Weather Service:[4][5] As the updraft pushes flattish cumulus clouds up & a horizontal vortex develops from differential updraft speeds... As the vortex climbs, it's caught in the faster horizontal winds aloft, & the middle part of the vortex catches the faster speeds with the ends being slower.