Spinning Twister Sisters Ask Dave a weather question

Dave Thurlow, Host

 
Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook. You may recall that scene in the movie "Twister" where two protagonists and a vehicle are spinning around on a bridge. They're trapped in between a pair of tornadoes dancing around each other like serpents. Hollywood took some dramatic license for this shot, but there is a grain of truth in the concept.

Photo by Homer G. Ramby

Many large tornadoes have several vortices, or circulations, rotating around one center. These multiple vortices can cause some of the tornado's worst damage because of the extra spin each individual vortex adds to the whole storm. It's a bit like that old amusement park ride, the Tilt-a-Whirl. Remember how it felt when your chair was spinning in the same direction as the ride itself? The spin of each cup was added to the spin of the whole ride, and it only took a few seconds for your stomach to figure this out.

The first person to speculate that tornadoes had multiple vortices was Ted Fujita, the legendary tornado researcher who developed the scale to determine tornado damage, such as F5. Scientists at the National Severe Storms Laboratory produced multiple vortices when they cranked up a tornado simulator. But nobody was able to prove their existence in the real world until 25 years ago this weekend. That's when the country's biggest tornado outbreak on record brought almost 150 twisters across the South and Midwest.

One of these tornadoes was captured on film near Muncie, Indiana, by Wally Hubbard, a freelance TV photographer, as he drove home from his regular job. Hubbard noticed something strange: there seemed to be several little tornadoes dancing around the big one. A few weeks later, scientist Ted Fujita came across the TV footage that confirmed his multiple vortex theory. The rest is tornado history.

Bob Henson is today's contributing writer. To see pictures of multiple vortices, visit our website at weathernotebook.org. Our show is underwritten by Subaru the beauty of all wheel drive with major support provided by the National Science Foundation.