Why green skies before a storm don’t always mean a tornado

Green skies are gonna clear up, put on a happy face …

Strong to severe storms are expected in the Austin metro area late Tuesday afternoon and evening. Large hail and damaging winds main threats but forecasters aren’t ruling out the possibility of a weak tornado.

You should stay inside during tonight’s storms. But if you’re out as they approach, or get caught in it, there is a chance — albeit small because it will be nighttime — that you could see something strange: green skies.

It’s a phenomenon so old that sailors from ancient Greece wondered about it, but it’s one that has been reported so often that meteorologists are certain it exists. But as far as the science of meteorology has progressed since ancient Athens’ heyday, it’s still not clear why the sky turns green, according to weather experts at Texas A&M’s Department of Atmospheric Sciences.

“The most popular theory is that thunderstorms contain a lot of water – often in the form of hail – and this water or ice tends to scatter green light during the strong updrafts that occur in severe storms,” said Brent McRoberts, a postdoctoral research assistant in the atmospheric science department. “That’s why many people say the sky appears green right before a hailstorm.”

The sky can also turn green before a tornado, McRoberts said. Green skies do not necessarily mean a tornado, though, and they may or may not contain hail. But they are almost always a sign that bad weather is on the way, said McRoberts, adding that the main point to keep in mind with green skies is: “You should take cover immediately.”

CaptureThe Statesman’s Amanda O’Donnell posted a blog earlier this month about how drone video taken near Wylie, where grapefruit-sized hail caused severe damage to many homes and vehicles earlier this week, made social media users curious about the strange color of the clouds. The Weather Channel reported that the green glow was from hail about to fall.


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