Wedge Tornadoes: Nature's Largest Twisters

New Orleans, Louisiana made weather news headlines in 2017 not because of a coastal Atlantic hurricane, but because of the New Orleans East tornado. Rated an EF2, this monster weather system touched down near the city in early February of that year. It left many asking, "What is a wedge tornado?" and wondering how such a large and strong storm could occur so early in the tornado season.

A wedge tornado is the name storm spotters use for a tornado that takes the shape of a wedge, or an upside-down triangle. Unlike narrow, column-shaped funnel tornadoes, the wedge tornado's straight, sloped sides make it look as wide, or wider, than it is tall.

Large, But Often Hidden in Plain Sight

Due to the size and width of wedge tornadoes, they are thought of as the largest and most menacing tornado type. It is so broad that at first glance it's not recognized as being a tornado. The base, or part of the storm that touches the ground, of a wedge tornado can be a mile or more wide, and often looks like low-hanging dark clouds to passersby. These "fat" storms often bear the lion's share of blame among tornado survivors, because they seem to strike without warning.

As if they weren't already difficult to see, wedges can also be "rain-wrapped." When this occurs, curtains of nearby rainfall encircle the tornado funnel, veiling the twister and further lowering its visibility.

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Why So Monstrous?

Thankfully, wedge tornadoes make up only a fraction of tornadoes. Roughly 2% to 3% of confirmed tornadoes from 1950 to 2015 have been wedge-shaped. Like ordinary-shaped tornadoes, these mile-wide monsters form when warm, moist unstable air collides with dry, stable air in a region of enhanced lift and strong vertical wind shear. The secret to their mammoth size is still somewhat unknown, but the formation of multiple vortices around the main funnel may help to expand the width of the storm's total wind field. 

Geographically, wedges are more common in the southeast, next door to the moisture-rich Gulf of Mexico, than elsewhere in the U.S. Clouds in this region also tend to hang at low levels in the sky, which means should a tornado form, its funnel will likely be short and stout, prerequisites for a developing wedge tornado.

Width Without Strength

Given their apocalyptic appearance, there's a misconception that wedge tornadoes will always be powerful tornadoes, but this isn't necessarily true. Wedge width is not always a measure of severity. There have been wedges that were rated as weak EF1 tornadoes, so clearly a tornado's size has nothing to do with its strength.

However, wide tornadoes indeed have a tendency to also be quite violent. At 2.6 miles wide, the May 2013 EF3 El Reno, Oklahoma wedge tornado is a perfect example. It holds the record as the widest tornado ever measured. A number of the most lethal U.S. tornadoes were wedges, including the May 2007 Greensburg, Kansas; the 2011 Joplin, Missouri; and the 2013 Moore, Oklahoma tornado disasters.

Other Tornado Shapes to Look For

Wedges are just one of several shapes tornadoes can take on.

• A "stovepipe" tornado has a long, cylindrical shape, and is named for its resemblance to a roof or chimney stove pipe.
• "Rope" tornadoes resemble strings or ropes because of the curls and twists in their long, skinny funnels. They can describe narrow tornadoes or signal a dissipating tornado. As the funnel lengthens, the winds within it are forced to weaken⁠—due to conservation of momentum⁠—and its circulation to shrink, a process called "roping out."
• Of course, the classic twister bears a cone shape, with the storm at its widest where it meets the clouds and a tapered base at ground level.

Resources and Further Reading

• Livingston, Ian. “Two Reasons We Have to Stop Throwing Around the Phrase 'Wedge Tornado'.” Capital Weather Gang, Washington Post, 23 Apr. 2019.