January 20, 2018

Newest Cloud Types Seen in the Pacific Northwest

In  March 2017, an updated International Cloud Atlas was released and several new clouds were added. 

One new cloud is Asperitas, characterized by a complex wave-like base.   This week (January 17th), James Dearman sent me this wonderful shot of an Asperitas cloud that he took near Vancouver, Washington (see below). 

Pretty amazing cloud, with undulations looking like a sea surface turned upside down.

Here is another example from Virginia:

These clouds result from wave-like motions in the atmosphere that distort a pre-existing cloud deck.   Such waves can be initiated by fronts, thunderstorms, or some other type of atmospheric disturbance.  Generally no precipitation or severe weather with these clouds--but they do look scary.

Folks normally don't think about it, but the atmosphere is full of waves.    Generally, the atmosphere is stable, meaning if you push an air parcel upward, it will want to return to where it started.  But like a swing set, the air parcel tends to overshoot and goes into an oscillation.  A pendulum is another example.

Another new cloud is one we have talked about in this blogCavum, or the hole punch cloud (see below).   These "holes" are produced when an aircraft goes through a cloud made of supercooled water (liquid water below freezing).  The passage of the aircraft through the cloud causes a transition to ice crystals, which subsequently fall out, leaving a hole.


  1. Very nice, as long as the ice crystals don't stick to the airplane!

  2. Curious...what do you mean by "New cloud type"? Are they just categorized or named different? Certainly these cloud 'types have occurred in the past.
    Mac Madenwald, Anacortes pangaeamac@hotmail.com

  3. As a kid I saw those clouds a few times before a snow--and called them stratoformis lenticularis--35 years later they finally have an official name, neat!

  4. The Seattle /Tacoma radar seems to be down a lot in the past few months. Is there a problem?

  5. Thanks for the shoutout. Great blog post!


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How unusual is it for aircraft to exceed the speed of sound?

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