The sometimes-eerie-looking "Hat" clouds -- officially known as lenticular clouds -- are no stranger to Mt. Rainier. But while to many it might just look like a cloud frozen in time, there is actually quite a bit of air movement involved in making the clouds.
KOMO News photographer Mitch Pittman was up hiking in the Cascades recently and managed to get this amazing time lapse video (above) of a lenticular cloud sitting atop Mt. Rainier. The video is a great illustration of the flow that goes into making the cloud's lens-type feature.
The clouds are formed when you have three ingredients: Warm, moist air that is just on the cusp of saturation, laminar flow (when you have winds constant with height -- as in little to no turbulence or shear) and something big to get in the way, like, say, the region's tallest mountain.
When the air flows over the mountain, it will create waves either atop the mountain, downstream, or both, where the air is now going up and down, and up, and down -- like ripples on a pond or waves on the ocean. When the air goes up, it cools a little bit and when conditions are on the cusp of saturation, that slight cooling is enough to create a cloud. When the air sinks back down again, an opposite drying effect occurs and the cloud disappears.
While to us it might look like the clouds are floating in place, in fact, the air is streaming through the cloud as it hovers there -- think of someone pedaling a stationary bike instead of just sitting on a bike and not moving.
And sometimes the effect propagates downstream from the mountain, making alien-type clouds appear to be hovering alongside the peaks, like this video from Edward Aites:
Atmospheric conditions needed to make the cloud are typically found a day or so before an approaching rain event -- thus the local know when you see a hat on Mt. Rainier -- it's just the mountain getting ready to keep its head dry!