Debunked: The Green Sky Hail Myth

An article in Scientific American, sent in by blog reader Scott, has debunked the myth that green skies indicate hail in thunderstorms -- kind of.

The scientists confirmed the green hue, but found that it had no relationship to the presence of hail or tornado in the storm, or even the color of the ground the storm was moving over.

The author, Frank Gallagher, has been a bit obsessed for this topic for many years. Check out this PowerPoint presentation on thunderstorm Colorimetry he did in 1998 on the same topic. The myth is certainly pervasive -- in fact he says that the Weather Channel Calendar in 1994 stated "...a green tint... is often a sign of nearby hail and perhaps tornadoes." And he also quotes historical anecdotes that go back 100 years.

In the end, the scientists confirmed the green hue but really couldn't explain it, but hypothesized that it was a combination of the blue hue in clouds due to light scattering) and the red hues at sunset.

Of course, green storms have been spied at times other than sunset, such as the nighttime photo on this page (Lightning in Charlottesville, VA on April 4th -- AccuWeather.com Weather Photo Gallery user taptap), so I don't think that we can say this topic is wrapped up.

We may never know. Apparently getting research funding was difficult due to the perceived useless nature of it, though I'd argue that I've seen money wasted on worse stuff, and if it had been found that it was indicative of hail, tornadoes, or something else, that would have been meteorologically significant.

PHOTO AT RIGHT: Tornadic storm in Minnesota in 2001 (weatherbum)