Jessica Sue Mills McGee
Location: Westminster, CO
Date: 28 June 2014
When strong stable air flows perpendicular to mountain ranges, an oscillation is created downstream of the mountains. These peaks and valleys in the air are trapped within the stable layer, and wherever there’s enough moisture, clouds can form. These clouds commonly appear in the mid-levels and are lens-shaped, appearing like flying saucers at times. They are called Altocumulus lenticularis and a particularly good example of this cloud type can be seen in the top right photo above. In the other photos, you can see the wave clouds over Westminster, located to the east of the Rocky Mountains. The strong zonal (west-to-east) airflow across the mountains created this beautiful sight at sunset while lower levels of the atmosphere remained dry.
Here is a diagram from the COMET program that helps show what we mean by oscillating air in a stable environment.