Last night, around 6pm, I was running with my dog around Magnuson Park in Seattle and noticed some awesome clouds.
The bottom of the cloud layer is deformed by waves and strange structures. It was so unusual that several people sent me photos, and the nearby National Weather Service office posted some photos (see some samples below).
Image provided by NWS Seattle Office
Image provided by John McBride
These beautiful clouds have an impressive name: Undulatus Asperatus. Often they are simply called Asperitas cloud.
You can get another view of these clouds from the SpaceNeedle PanoCam at 6 p.m. Quite scary!
Or you can watch from space, using the NOAA/NWS GOES satellite 35,000 km above the surface (I’ve put a red arrow pointing at Seattle’s Magnuson Park), You can see the shield The giant cloud of the frontal system is moving at this time. And so many ripples like waves in the clouds.
Asperitas clouds are one of the newest additions to the cloud classification system, joining its more familiar cousins about a decade ago.
The limited research I have seen suggests that Asperitas clouds are involved Atmospheric gravitational waves, waves in the atmosphere are similar to water waves on the ocean surface. These waves can distort cloud bases in dramatic ways.
Yesterday, late in the afternoon, a frontal system was moving in and winds aloft were strengthening. Looking at the Seattle PanoCam a few hours ago (4:30 p.m.) showed many lenticular clouds in the sky (they looked like flying saucers!). Clearly, there is a lot of wave activity aloft: the wave-filled skies created by the Olympics interact with the enhanced currents.
Here is a diagram of such a mountain wave.
As the front passes, the clouds associated with the front’s motion are distorted by all the mountain waves downstream of the Olympics, creating a dramatic display of Asperitas clouds.
I think this is a reasonable theory of what happened, but there are certainly other ideas.
