A Summer of Beautiful Cirrus Clouds

This has been an interesting summer in many ways, with a persistent offshore upper-level trough resulting in temperatures averaging a bit higher than normal, but with a lack of major heatwaves. 

But there is more.  The offshore upper-level trough has produced upward motion in the upper troposphere (roughly 15,000 to 35,000 ft) that has produced ice clouds.

These are cirrus clouds of various forms, and they are often very beautiful.  Let me share a few pictures with you.

Below is a picture taken last night near sunset.  Ice crystals are actually falling out of some of the cirrus clouds and bending back due to the weaker winds at lower levels.

These features are called fallstreaks.  Often called mare’s tails.

Or if you want something really fancy, here is a circulus cirrus cloud complex with a fallstreak in the middle.   Could be mistaken, perhaps, for a UFO.

By the way, one way you can tell you are looking at an ice crystal cloud is that the boundaries of the cloud are fuzzy and not sharp.

Sometimes circus forms in complex linear features:

And if there is enough change in wind speed with height, the cirrus can be distorted into wave-like features associated with the impressive-sounding name, Kelvin-Helmholtz instability:

What do cirrus clouds look like from space?   Here is a recent example showing lots of cirrus clouds over the South Sound.

Finally, this is one type of ice crystal cloud that is less frequent over western Washington than over the eastern half of the U.S.:  cirrus anvil clouds associated with vigorous thunderstorms.   I did catch an example of one associated with a thunderstorm over the Cascades (below).  You see the flat upper portion of the thunderstorm….that is the cirrus anvil.

Enjoy your cirrus viewing.


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