The Washington PostDemocracy Dies in Darkness

How a mesmerizing cloud — stacked like pancakes — hovered over Mount Shasta

The shimmering vaporous disk spent all evening hanging over part of California

Video taken on Jan. 22 shows a series of lenticular clouds swirling around the top of Mount Shasta in Northern California. (Video: Robert Renick)
4 min

Last week, the internet gawked over a ruby-red, cinnamon-bun cloud that hung in the skies over Bursa, Turkey. This week, the same phenomenon was sighted in California — except this time it looked like a magically floating stack of pancakes.

Videographer Robert Renick captured a time-lapse video Sunday of a self-regenerating “lenticular” cloud that spent the late afternoon and evening hovering atop the 14,179-foot-tall summit of California’s Mount Shasta. The mountain in northern Siskiyou County, Calif., is a prolific producer of lenticular clouds — often providing stunning opportunities for photographers based in the nearby towns of Weed and McCloud.

A similarly placed lenticular cloud drew attention in 2020 as it stood against the morning sky, basking in the colors of sunrise.

Lenticular clouds are a common ornament of isolated mountains, often resembling a cap or hat. Some can hover for hours on end, even when the rest of the sky is clear.

In the case of Sunday’s event, the time-lapse video depicts the lenticular cloud staying firmly in place for much of the afternoon, even as strong winds nearing 70 mph blew up and through the mountain continuously. That steady stream of air from below is key to its formation and explains how it remained weightlessly in place for so long.

Dissecting its formation

Winds were light at the surface across Northern California on Sunday afternoon. The air was dry and layered, and the atmosphere was stable. That meant there was little upward motion, and air parcels didn’t have any reason to move vertically. Instead, all the invisible layers in the atmosphere were settled.

That’s where Mount Shasta comes in.

The mountain interrupted that otherwise unperturbed environment. Ascending winds were out of the north, rushing southward at high speeds. In the absence of a mountain, that wouldn’t have resulted in a cloud. The air would still have been layered and stable but moving horizontally.

By poking into that layer of strong winds, however, Mount Shasta acted like a stone in a river, interrupting the flow and introducing turbulence. That forced air from below to move up the north face of the mountain, where the otherwise dry air was cooled to its dew point. That left the air saturated ― forming a cloud — which then dried up on the south side of the mountain as the air descended, in turn eroding the cloud. The result? A cloud only atop the mountain. In fact, roughly half a dozen layers of atmosphere were involved, which is why it’s easy to spot five or six “tiers” in the quasi-stationary lenticular cloud.

Looking at the data

We can review data from a nearby weather balloon launch around 6 p.m. Sunday evening in Medford, Ore.

It appears there was a very dry layer between roughly 6,700 feet and 10,000 feet, with relative humidities as low as 4 percent and an enormous difference between temperature and dew point. The greater the difference between those two values, the drier the air.

But then something interesting happened. At a little over 10,000 feet, the air suddenly became moister, with temperature (29.3 degrees) and dew point (23.5 degrees) a bit closer together. The air was still not at saturation, since the two numbers weren’t equal.

What probably happened was that the air was forced up to the top of the 14,179-foot summit before it could curl back downward. As it was lifted, it was forcibly cooled down to about 18.5 degrees. That meant the air from 10,000 feet was chilled down to its dew point (23.5 degrees), reached saturation (forming a cloud) and then continued shedding moisture while being saturated (forming a cloud and perhaps precipitation in the form of snowfall).

That checks out in the video ― it’s easy to see the exact “lifting condensation level,” or layer at which the air becomes saturated. You may even catch a glimpse of what appear to be tendrils of snow blowing downwind from within the cloud. The dry air below, meanwhile, afforded clear viewing, since no other clouds were able to form.

Northern California has been plagued by active weather as of late, with no fewer than nine “atmospheric rivers” in 3½ weeks dumping 32 trillion gallons of water on the Golden State. Shasta Dam, near Mount Shasta, received 26.63 inches of rain between Christmas and Jan. 20 — more than 2½ times the average. With freezing levels between 6,000 and 8,000 feet, the uninhabited volcanic summit of Mount Shasta probably received at least 25 feet of snow within the same window.