And last week, as high clouds streamed in overhead, a good example of this feature was captured by weather videographer extraordinaire Greg Johnson of Skunk Bay Weather.
During a sundog event, areas of light are seen on both sides of the sun (see example below). These are the "dogs." Sundogs are also called "mock suns"
The ancients thought that sundogs were ominous signs, foretelling events such as the death of kings. Today we know that sundogs generally occur when the sky is filled with a thin veil of ice crystal clouds, generally cirrostratus.
Now let me show you a video captured by Greg Johnson from his location in northern Kitsap County around 6:30 AM last Wednesday. From his camera, you only see one of the dogs.
The sky at the time of sun dogs was full of high ice crystal clouds, called cirrostratus. You can see the extensive veil of such clouds from the visible satellite picture taken about this time (see below):
Why sun dogs?
They occur when ice crystals in the clouds--shaped in six-sided plates--are oriented roughly horizontally. With that orientation, they preferentially bend the light by 22 degrees, creating two areas of light (22 degrees on both sides of sun), as illustrated by the figure below.
Ice crystals that are smaller and tumbling about create circular halos.
As shown in the picture above, many sundogs have rainbow colors as well, something also illustrated in the picture below.
These colors are produced by dispersion, the breaking up of visible light into its component wavelengths, as it passes through the ice crystals, not unlike what happens in a prism (see below).
Cirrostratus and associate halos and mock suns are often a sign of an approach weather system, such as a front or cyclone. Thus, although it may not foretell the death of kings, it can suggest the end of nice weather.
Most of the time, you can not see the air move. You can feel it, but the complex, turbulent motions are invisible to you, except when it interacts with leaves and branches on trees and plants. But for a few weeks of the year, the sky is full of small, cotton-like tuffs that like a natural MRI machine reveals the complex three-dimensional motions of the atmosphere. Cottonwood season. And we right in the middle of it. Being cottonwood aware is of particular value this year. It reveals the active dispersion and movement of air that makes the outdoors essentially COVID safe, and thus should be of some comfort for those nervous about transmission outside. Cottonwood seeds are embedded in small cotton-like fibers. A million seeds weigh about 3 pounds. Yes, each seed and tuff weights about .000003 pounds. And that fact, plus the cottonwood tuff, means that these seeds fall VERY, VERY, VERY slowly. So slowly that they are excellent markers for the three-dimensional flow of the
During the past 24-hours, there have been a few lightning strokes over the region (see below) but nothing to write home about (see below). It turns out that the Pacific Northwest and the remainder of the West Coast have some of the lowest frequencies of thunderstorms in the entire country (see below). But why? My podcast provides the answer. And I also give the weekend forecast....and I think most will like what I have to say. To listen to my podcast, use the link below or access it through your favorite podcast service. Some major podcast servers: Like the podcast? Support on Patreon
While the Northwest has been drier than normal, it has been drenching wet a few hundred miles to the north. An unusually strong atmospheric river ....a long current of moisture stretching southward to the subtropics...has been in place for days, bringing large amounts of water vapor to Alaska. And the atmospheric river will be in place for several more days, slowly moving southward. To illustrate, the scale and beauty of the atmospheric river, here is a water vapor satellite image for 11 AM today. The lighter areas have more water vapor. You can see the current of moisture extending from near Hawaii into central BC. This current is the result of low pressure over the Gulf of Alaska and high pressure offshore of California. A forecast of total water vapor content in the atmosphere for 11 PM tonight shows a healthy atmospheric river (white and blue colors indicate the higher amounts of moisture). As this atmospheric river slams into the mountainous West Coast, the air is forced to
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