2/23/13: Timelapse, The Calm Before the Storm

Prior to the arrival of the largest winter storm of the season thus far, this short time lapse contains two sequences, one showing a  standing lenticular cloud moving off the Front Range in the morning, the second of the day’s sunset, with the rising moon disappearing into the darkness of the leading edge of the storm.

For those of you living along the Front Range, you’ve undoubtedly heard the local news talking about the ‘mountain wave’ clouds that are so common around here in Spring and Fall. Altocumulus Standing Lenticular (ACSL) clouds are created when moist air in the middle atmosphere hits the mountains and rises, cooling to below dewpoint, and increasing in velocity (a la the ‘venturi effect’). The cooling of the air below the dewpoint condenses the water in the atmosphere and a cloud is formed, quite often directly over the edge of the foothills, like Golden and Boulder. These ACSL clouds are relatively stationary compared to the air movement within them, and you can see this in the video, especially at the leading edge (right side) of the cloud in the first sequence. If you watch closely, you can see that the wisps of cloud as they are created move into the cloud quickly, although the cloud remains nearly stationary. In the case of this particular cloud, it behaves as they so often do, moving downstream toward Denver and then mostly disappearing by noon or so.

More than you ever wanted to know about lenticular clouds, I know…