Mt. Rainier puts on spectacular show with multi-layered lenticular clouds

Lenticular clouds form over Mt. Rainier on Dec. 12, 2017 (Photo: Tim Durkan Photography)

Any show of lenticular clouds over Mt. Rainier has the potential to be dramatic, but Tuesday afternoon's show has to be among the best, (but still behind this epic event.)

Several of our #SoNorthwest Legion of Zoom photographers managed to capture the incredible display, which not only featured the alien saucer-like cap cloud on top of the mountain, but a tower of 6-7 other clouds downstream that were lined up like a stack of pancakes.

The cloud, known as a "lenticular cloud" is 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 downstream 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 -- the cloud is just showcasing the right spot in the atmosphere where the air is undergoing its lift and sink. Sometimes this occurs right over the summit, giving the mountain a hat.

In this case, Mt. Rainier caused turbulence downstream at several layers, each wave creating its own cloud as it rose up and cooled enough for condensation.

The clouds are usually a sign of approaching rain within 24 hours as these conditions with an atmosphere right on the edge of condensation usually precede an incoming weather system. But Tuesday's event was one of the rare times the predictor failed -- it worked in reverse instead. Earlier in the day, a weak system had pushed and as it left, the lingering moisture in the atmosphere was enough to trigger the dramatic clouds.

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