Weather Whys; Rainbows

This is weather-wise. Rainbows amaze and delight those who see them. Some find religious significance in the colorful bands in the sky. Others search for the pot of gold that's supposed to be at the end of a rainbow. And still others see the rainbow as a forecasting tool. The familiar rhyme, rainbow in morning, sailors take warning, rainbow by night, sailors delight is one of the relatively few old weather legends which holds water, so to speak. Rainbows appear when sunlight illuminates part of the atmosphere that's full of water droplets like rain or even the spray from a garden hose. That's because of a phenomenon known as refraction. When sunlight hits a water droplet at just the right angle, some of the light is bent or refracted within the drop, and then it's reflected out. It, which is nearly white, contains light of all colors from red to violet. Each of those colors is refracted out of the water droplet at a different angle, allowing us to see the component colors separately.

But since the colors do spread out, only one of them will reach your eye from any given raindrop. The entire rainbow is created by the combination of those colors coming from a lot of raindrops. Now, here's the reason the old saying often holds true. For you to be able to see a rainbow, the sun must be behind you and the rain in front of you. So if you see a rainbow in the morning, the rain must be west of you. Since weather systems in the mid-latitudes move generally from west to east, that could mean there's rain moving your way. On the other hand, if you see a rainbow at night, that means the rain is east of you, so that could point to fair weather ahead. A sailor's delight indeed. Otherwise is produced with the assistance of the National Weather Service Forecast Office and the National Severe Storms Laboratory, both in Norman, Oklahoma. Our writer is Christine Harmer, our editor is Brian Waukey. For weather-wise, I'm Crue Barlow.