A horseshoe cloud is a relatively uncommon meteorological phenomenon which manifests as a

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may ...

in the shape of a horseshoe or inverted letter "U". They occur when a

horseshoe vortex The horseshoe vortex model is a simplified representation of the vortex system present in the flow of air around a wing. This vortex system is modelled by the ''bound vortex'' (bound to the wing) and two '' trailing vortices'', therefore having ...

deforms a cumulus cloud. The clouds are relatively short-lived. Horseshoe vortex clouds are a form of "fair-weather"

funnel cloud A funnel cloud is a funnel-shaped cloud of condensed water droplets, associated with a rotating column of wind and extending from the base of a cloud (usually a cumulonimbus or towering cumulus cloud) but not reaching the ground or a water su ...

and are similar to the shear funnel type of funnel cloud. A March 2018 instance was explained by the United States

National Weather Service The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...

: These clouds do not occur often because all the conditions that must be met rarely occur together.

References

Cloud types {{Cloud-stub