Colynn Kerr recently sent us his timelapse video taken in Alberta, Canada. It is a film of lenticularis clouds at sunset, showing how the formation appears in a ‘standing wave’ of air. As it rises to pass over a mountain, an airstream can take a rising and dipping path in the lee of the peak, with a lenticularis cloud forming at the crest of the wave. You can see the flow of air in the video by the movement of the clouds around the lenticularis, with the lenticularis remaining fixed in place at the crest of the standing wave.