Lenticular UFO clouds and other spectacular cloud formations

Sometimes likened to UFOs, lenticular clouds are usually created by gravity waves. Bright colours (or irisation) are sometimes seen along the edge of lenticular clouds...

...Lenticular clouds are often shaped like flying saucers, leading to people reporting UFO sightings

Mammatus clouds, meaning "breast clouds", are associated with strong storms...

...They are often associated with tornados and are seen in warm summer months

Polar Stratospheric or Nacreous clouds generally form at very low temperatures, below minus 78 °C

Polar mesospheric or Notilucent clouds are made of crystals of water ice and are the highest clouds in the Earth's atmosphere, located in the mesosphere at altitudes of around 76 to 85 kilometres

Kelvin-Helmholtz wave clouds are formed when there are two layers of air moving at different speeds and in opposite directions

Roll clouds over Sydney. They typically occur in the lower atmosphere ahead of a storm front

Roll clouds

Morning Glory clouds are a specific and more unusual type of roll clouds. They are seen most often on the Cape York Peninsula, in a remote part of Australia

Cumulus clouds poke through dust associated with the Saharan Air Layer

Sarychev Volcano (Kuril Islands, northeast of Japan) erupts in this picture taken from the International Space Station in June 2009. The plume appears to be ash and steam. It cleared a circle in the cloud deck

Hurricane Bertha seen from the International Space Station