Virtual twister reveals possible source of tornado longevity

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A rotating updraft within this 20-kilometer-high thunderstorm sired a violent tornado. The twister, which looks quite small  compared with the rest of the towering storm, packed winds at over 320 kilometers per hour and left behind a long trail of devastation. Or it would have, had the storm been real.

This realistic visualization of a supercell thunderstorm was honored at the Extreme Science and Engineering Discovery Environment conference in St. Louis in July. The underlying computer simulation, which calculates how pressure, moisture and heat conspire to create megastorms, is the first to successfully reproduce a long-lived EF5 tornado, the most severe designation of twister. The simulation could help explain why some tornadoes linger for hours after forming, says cocreator Leigh Orf, an atmospheric scientist at the University of Wisconsin–Madison.

Orf’s team spawned the virtual storm in conditions resembling those that bred an EF5 tornado near El Reno, Okla., on May 24, 2011. The simulation revealed that descending pockets of cool air, which form when raindrops evaporate, hit the ground and curl upward, creating vortices. The storm sucks in these vortices, which keep the tornado spinning.

Storm chasers may be able to verify that these vortices swirl near real tornadoes, Orf says. 

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VIRTUAL TORNADO  Researchers bred their own titanic twister using a supercomputer simulation that digitally replicated the temperature, humidity and pressures that spawned a real-life tornado in 2011. A graphics renderer added photorealistic light and shadows.

Credit: David Bock