Weather Blog

Sunshine trick gives Sequim horizon a rather bizarre glow

Sunshine trick gives Sequim horizon a rather bizarre glow
Anti-crepuscular rays seen over Sequim, Wash. on Feb. 26, 2013. (Photo: Judy Davidson)

Did everyone in the Puget Sound region just turn on their lights at the same time?

No, but forgive those up in Sequim on Washington's Olympic Peninsula for getting that impression as the sun put on a rather puzzling display of light -- on its opposite horizon -- as it set Tuesday evening.

These photos from Judy Davidson show what appear to be a glowing light from the distant east, but what she saw were called "anti-crepuscular rays".

(For those who like to read aloud in your head, here is how to pronounce it).

You're likely more familiar with the regular crepuscular rays that some have given the informal term "Fingers of God" when you see rays streaming down from a break in the overcast, like seen in this video from Silverdale, Wash. :
 

But the "anti-" ones form on the opposite side of the sun. According to the always informative Atmospheric Optics site, "anticrepuscular rays converge in the opposite direction and you must have your back to the sun or sunset point to see them."

The rays are formed by sunlight filtering through breaks in the cloud, and dust or other particles in the air scatter the sunlight a bit to where they become visible. But unlike the more common crepuscular rays that point toward the sun, these point away from the sun, the Optics site said.

The rays actually go in straight, parallel lines but appear to convergence on the horizon due to perspective -- just like a long, straight road appears to converge into a narrow triangle as it nears the horizon:


Photo: Flickr user Gabriel White (CC License)