The Weather Notebook: Midnight Tornadoes

Midnight Tornadoes
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On the night before Valentine's Day this year, Georgia had a deadly tornado outbreak, one of its worst in more than 50 years. The twisters struck at midnight, catching many folks asleep. Mobile homes were tossed to pieces, and 13 people died. Hi, I'm Dave Thurlow for the Mount Washington Observatory and this is The Weather Notebook.


A tornado seen in the distance as dusk settles over a farm. NSSL Storm Spotter's Guide

When this story hit the news, it sounded like a freak event. Tornadoes in the middle of the night? Don't twisters need the warmth of a spring or summer afternoon to grow? Well no. Actually, you can get a tornado at 10 pm, 2 am, or 4 pm. A twister doesn't care about the clock: it only needs the right ingredients.

The key for getting nighttime tornadoes is to have a batch of very moist air in place, which keeps the air from cooling down overnight. Then stir it with energy from extra high-speed winds 3 miles above the ground.

Many people have been jolted by middle-of-the-night or early morning twisters. One of them ripped across 47 miles of central Oklahoma at 2 AM on April 30, 1970. An even worse blow hit Oklahoma City at 10 AM on November 19, 1930, just a week before Thanksgiving. This small but intense twister killed 23 people, including five students who scrambled for shelter just as the storm hit.

The most frequent location for nighttime tornadoes is the Deep South, because the nearby Gulf of Mexico helps to provide warm, moist air even in midwinter. That way, you don't need sunlight to make the conditions volatile.

Thanks to Bob Henson, today's contributing writer. The Weather Notebook is underwritten by Subaru, the beauty of all wheel drive.