Multiple Vortex Tornado
Many tornadoes contain smaller, rapidly spinning whirls known as subvortices, or suction vortices; but they are not always as clearly visible as in this big tornado near Altus OK, on 11 May 1982. Suction vortices can add over 100 mph to the ground-relative wind in a tornado circulation. As a result, they are responsible for most (if not all) cases where narrow arcs of extreme destruction lie right next to weak damage within tornado paths. Subvortices usually occur in groups of 2 to 5 at once (the 6 or 7 evident here being uncommon), and usually last less than a minute each. Tornado scientists now believe that most reports of several tornadoes at once, from news accounts and early 20th century tornado tales, actually were multivortex tornadoes. However, on rare occasions, separate tornadoes can form close to one another as satellite tornadoes.
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