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That was some sunset last night. Here’s what helped.

Updated Sept. 25, 2019: Last night’s sunset begged to be photographed. Those were wave clouds, which are rows of cirrocumulus and altocumulus clouds in an undulating pattern, according to the National Oceanic and Atmospheric Administration.

Sometimes called a “mackerel sky” because they resemble fish scales, these types of clouds often promise a change in the weather.

“Mackerel sky, not 24 hours dry,” the saying goes.

The display was just one kind of cloud we see here in the Northwest. Here’s what I wrote for a 2015 issue of Bellingham Families magazine about the others:

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Clouds are among the most common of everyday sights, a serendipitous marriage of poetry and physics.

A child might see faces and shapes in clouds’ ever-changing formations, while a scientist would predict a heavy storm brewing.

Clouds appear light and fluffy, but in reality the average cumulus clouds contains more than 1 million pounds or water or ice.

“A cloud is basically a drop of water,” said Paul Thomas, a lecturer in the Geology Department at Western Washington University. Thomas, who studies climate change, teaches meteorology classes at WWU.

Various factors affect the shape, size and color of clouds, he said. Essentially, what we’re seeing is sunlight scattered and reflected through the droplets.

“Usually that has to do with the way they absorb light, the size of the droplets and their thickness,” Thomas said.

Clouds fall into four main groups, he said, with several subclassifications, mostly based on where the cloud is found in the sky, from low to the ground to 30,000 feet high - the realm of commercial jetliners.

“Oftentimes, when you have weather coming in, or a front, usually you’ll see high clouds,” Thomas said. “What you see is dependent on the process that’s doing lifting,” from factors such as topography (mountains) to rising and falling temperatures.

Environmental and energy journalist David Biello, writing in Scientific American magazine, said clouds involve a complex interplay of fluid dynamics, turbulence, convection and mixing. They’re a visual example of what teachers call the “water cycle” - evaporation, condensation and precipitation.

Water evaporates from lakes, rivers and oceans; it condenses into clouds; and it falls to the ground as rain or snow.

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The sunset on Tuesday, Sept. 24, 2019, from Chuckanut Drive in Bellingham, Wash., was spectacular. It featured a wave cloud, which are rows of cirrocumulus and altocumulus clouds in an undulating pattern. Rod Koenig Courtesy to The Bellingham Herald
Robert Mittendorf covers civic issues, weather, traffic and how people are coping with the high cost of housing for The Bellingham Herald. A journalist since 1984, he’s also a volunteer firefighter for South Whatcom Fire Authority.
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