A Short Circuit for Tornadoes

Though meteorologists now know enough about tornadoes to predict with reasonable accuracy when they are likely to occur, they are powerless to prevent the deadly funnels from forming and cutting their swaths of destruction. Help may be on its way. A NASA scientist has conducted laboratory tests suggesting that tornadoes are electrically driven phenomena that can be dissipated simply by shorting them out.

Physicist Vernon Rossow likens a tornado to the rotor of an electrostatic motor, which turns as it transfers electric charges between a positive and a negative electrode. Much the same happens, he theorizes, when a region of positively charged water droplets form near another region of negatively charged droplets in storm clouds.

If the electrical potential, or voltage difference, between the electrode-like regions becomes great enough and there is sufficient cloud turbulence, regions begin exchanging streams of charged droplets. When two of these counter-flowing streams--which move as fast as 500 m.p.h.--are within a quarter to half a mile of each other, the droplets act as an electrostatic motor rotor. As they whirl, they whip the surrounding air into the familiar and dreaded funnel.

To test his theory, Rossow passed a mixture of steam and cool air between two oppositely charged wire grids in his laboratory at NASA's Ames Research Center in California. As the cold air condensed the steam into visible droplets, a tiny, 4-in.-high tornado came into view. But when voltage was removed from the grids, the miniature whirlwind promptly died away.

Assuming that a life-sized tornado could also be stopped by equalizing the charge on adjacent regions in storm clouds, Rossow proposes a novel experiment. Fine wire could be wound into a projectile and fired through tornado-spawning clouds. After the projectile leaves the cannon, a parachute-like plate attached to one end of the wire would pop open. It would pull on the wire, causing it to unravel from the speeding projectile.

By connecting the oppositely charged cloud regions, the wire would make a meteorological short circuit. If Rossow's theory is correct, lightning would flash between the regions, vaporizing the wire, equalizing the charge in the regions and robbing the tornado of the energy needed to sustain it.

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