LOUISVILLE, KY (WAVE) - They have been mistaken for flying saucers throughout history, and even a stack of pancakes by the hungry, but lenticular clouds are far from being unidentified flying objects. I promise they have nothing to do with aliens.
Altocumulus Standing Lenticularis (ACSL) or as they are more commonly known, lenticular clouds are formations caused by wave-like motions in the atmosphere. They are often found on hilly or mountainous areas.
Lenticular clouds are different from other clouds because they don’t move. They typically form when stable, fast-moving air is pushed up over a barrier such as a mountain. The air creates a parade of waves, think ripples formed when water flows around or over a rock. The air cools as it rises towards the crest of the wave and then sinks since colder air is heavier than warm air.
When enough moisture has reached the top of the topographic barrier, water will condense and lenticular clouds will form where the air is rising in the peak the air flow waves. As the air sinks back down into the wave's trough, the cloud may evaporate into water vapor. While winds are howling through the cloud it appears to stand still because the clouds will continuously form in the wave's crest and just dissipate just downwind.
ACSL is most often seen in the winter and spring when upper-level winds are strongest. While most often seen in mountainous areas, ACSL can form over flat land if a front causes enough wind shear.
There are multiple types of lenticular clouds; the differences are mainly based on altitude. They are altocumulus standing lenticular (ACSL), stratocumulus standing lenticular (SCSL), and cirrocumulus standing lenticular (CCSL). The video below shows altocumulus standing lenticular clouds forming over Reno, Nevada.