Not A UFO


Lenticular Cloud over Harold’s Cross Dublin Ireland, June 2015 (photo from Wikimedia Commons)

Strange as it looks, this fluffy white object is not a UFO (Unidentified Flying Object), it’s a special cloud.

Lenticular clouds form when the wind blows horizontally toward a fixed object that forces the air to rise and fall in a wave. If the air is moist it condenses at the crest of the wave and forms lenticular clouds at the top. The diagram below shows the wind flowing over a mountain, forming two mountain-shaped waves and lenticular clouds at peaks A and B.

Lee waves and windows (image from Wikimedia Commons)

Despite their calm appearance, the air around these clouds is very turbulent. Glider pilots ride the updrafts on the windward side but the downdrafts are deadly for everyone. This Weather Channel video explains more.

Because we don’t have mountains, lenticular clouds are rare in Pittsburgh. You have to travel to see a mountain wearing a hat.

Low lenticular clouds near Cook Inlet south of Homer, Alaska (photo from Wikimedia Commons)

(photos from Wikimedia Commons; click on the captions to see the originals)