Sure Sign Of Rain Ask Dave a weather question

Dave Thurlow, Host

 

One of the most reliable signs of rain is a ring of light around the sun or the moon. Hi, this is Dave Thurlow for The Weather Notebook. When you see a ring around the sun or moon, a solar or lunar halo, you can pretty much count on a rain or snow falling within 24 hours. Before the storm arrives, it sends out an icy warning flag.

Photo: Ronald L. Holle

This warning flag is a thin layer of clouds, at about six miles above the earth, where it's around 50 below zero. These high clouds are made of ice crystals instead the water droplets found in warmer clouds close to the earth. The ring around the sun or moon, the halo, is simply sunlight or moonlight sparkling off ice crystals in the high clouds. The ice crystals that reflect the light are six-sided, sort of like snowflakes. Their geometry causes the reflected moonlight or sunlight to concentrate in a circle or a ring.

Photo: Oliver Staiger

The high clouds that produce this effect are there in the first place because of strong winds that blow from west to east, 5 miles or so above the earth. These clouds are blown in from a storm, which is well to your west, and because storms move from west to east the storm will follow the path of these winds and will show up in your neighborhood in about 24 hours.

If you have any weather question call us at 1-888-724-6001 and just for asking we'll send you a free cloud poster. That's 1-888-724-6001. For a look at a halo check our web site at mountwashington.org. The Weather Notebook is produced by the Mount Washington Observatory, with support from Subaru -- the beauty of All-Wheel Drive and The National Science Foundation.