A rare cloud type spotted in Livingston, Montana, recently has drawn the attention of meteorologists nationwide.
The horseshoe vortex cloud is one of the hardest cloud types to find - and especially tough to photograph - as it generally vanishes in less than 15 minutes.
Sarah Tabor, a high school biology teacher, snapped several photos of the UFO-looking cloud on Sunday afternoon.
Horseshoe clouds require wind shear, wind speed or direction changing with height, to form. A cumulus cloud moves into an area with rising warm air known as thermals.
As the cloud moves over these thermals, the horseshoe cloud begins to take shape.
The air rises faster where the air is warmest, at the center of the thermal - thus causing the middle of the cloud to rise faster than the sides of the cloud.
With varying wind speeds, the cloud does have some spin to it, similar to a dust devil or waterspout, hence the name vortex.
Horseshoe vortex clouds typically occur during the afternoon when the sun is heating the lower levels of the atmosphere allowing for these thermals rise.
Legend has it horseshoes facing downward are good luck - here's hoping it brings us some rain and snow!
