Extraordinary weather phenomenon: the double tornado

The tornadoes are among the phenomena weather report spring and summer classics: there are an average of 1,000 a year in the United States, the most tornadic country in the world, and 20 to 50 per year in France. These whirlwinds which form under the thunderstorms the most powerful, supercells, are sometimes destructive. But, in some cases, it happens that the tornado does not happen alone, but in a double or even triple way! These “twin tornadoes” are photographed every year or so in the great American plains, and sometimes in Canada. In June 2014, a double tornado leveled 75% of the town of Pilger in Nebraska (USA).

According to some shots, it even appears possible that it was a triple tornado with 3 simultaneous vortices, therefore under the same storm: the first vortex lasted an hour, the second a few minutes, and the third (which did not not been officially confirmed) would have lasted only a few moments. By looking at the pictures and videos closely, we realize that the 2 or 3 tornadoes are also accompanied by multiple snorkels : these are the beginnings of additional tornadoes that do not touch the ground.

Tornadoes and waterspouts can occur in families

The double or triple tornado phenomenon is part of what are known in the United States as “tornado families” (tornado family): we also find this same type of multiple vortices in the case of waterspouts, tornadoes that occur on water, in the sea or on a lake. Multiple waterspouts are much more common than twin tornadoes, and occur regularly, especially in the Mediterranean. The number of possible waterspouts apparently has no limit as some photographers have been able to capture 5, 6 and even up to 9 simultaneous waterspouts side by side under the same storm.

As in the case of tornadoes, they are not all of the same intensity. The first is generally the most powerful and the most durable, the others are weaker and more ephemeral.

Twin tornadoes likely responsible for historic disasters

Why so many whirlpools under a storm? The event is mainly explained by the extreme power of the storm, and by the wind shears. It is possible that large historical disasters, such as the “Tri-state tornado” that killed approximately 700 people in March 1925 in the United States, could be explained by multiple tornadoes.

“Twin tornadoes” are sometimes confused with a different phenomenon: the multiple tornado vortex. In this case, a main tornado is surrounded by several small, very thin tornadoes, barely visible vortices, which revolve around the larger one and which do not necessarily touch the ground.

“Twin tornadoes” are different because they bring together two or three aligned tornadoes, of similar sizes, and which touch the ground: they are therefore doubly more dangerous.