November 7, 2009 in Washington Voices

For cloud-watchers, these are the dog days

Michelle Boss
 

I have been seeing a rainbow of colors in the sky lately, but they haven’t been the result of a passing rain shower.

Late in the afternoon, when the sun is low in the sky and cirrus clouds are present, one can often make out this colorful display right through the cirrus clouds themselves. The phenomenon is called a “sun dog,” and occurs when sunlight is refracted, or bent, by ice crystals. Cirrus clouds are those clouds that are often wisplike in appearance, and reside high in the atmosphere beginning around 16,000 feet. They are made up entirely of ice crystals. When light passes through these ice crystals, many different optical effects can occur, depending on the angle of the sun, and the shape and orientation of the ice crystals.

The sun dog, sometimes called a “mock sun” or parhelion, is one of those effects, and can be seen as a streak of colors (or sometimes just a bright spot) on one or both sides of the sun, and at the same elevation. Along with sun dogs, another similar optical effect is called a halo, which can be seen around either the sun or the moon. Since cirrus clouds are often (but not always) produced by the lifting air ahead of a low pressure system, a visible halo has been noted as a harbinger of foul weather. The old saying goes something like, “Halo ’round the sun or moon, rain will be a-fallin’ soon.”

As average temperatures continue their downward slide throughout this month, it’s more likely we’ll be talking about snow than rain. Average highs now are only in the mid-40s, while average lows have slipped below freezing into the lower 30s. A chilly, but wet October went a long way in making up what was a pretty substantial precipitation deficit, at least for Spokane. Spokane saw a whopping 2.3 inches of rain in October, bringing the annual precipitation total so far of 12.25 inches to within .17 inches of normal (as of Nov. 4).

Coeur d’Alene, unlike Spokane, had not been particularly dry, and saw nearly 4 inches of rain in October. At 21.08 inches of precipitation (as of Nov. 4), Coeur d’Alene is about 11/2 inches above normal for the year. Both Spokane and Coeur d’Alene saw their first real snow back on Oct. 29 (a record .4 inches for Coeur d’Alene), though it officially went on the record books at the Spokane airport as less than .01 inches – called a trace – which as far as snow records are concerned, is the same as none.

Michelle Boss can be reached at weatherboss@comcast.net

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