Most thunderstorms develop from updraughts of rising air, with the most violent and speedy ones called supercells. These long-lasting storms are rare but deadly – they can unleash havoc in the form of whirling tornadoes, giant hailstones, punishing winds, and flash floods. Take cover!
Earth experiences about 45,000 thunderstorms a day, but only a few of these are supercells, the worst of all storms. Created by rapidly rotating updraughts of warm, moist air, these super storms carry huge amounts of water and bring extreme weather. The top of the thunderclouds can reach as high as 16 km (10 miles) into the air, while the base may be only 500 m (1,640 ft) above the ground.
Thunderstorms are formed by warm updraughts rising to create cumulonimbus clouds. Cold rain drags air down, creating a cold downdraught. When there is more downdraught than updraught, the storm fizzles out. In a supercell the updraughts and downdrafts are in balance, so the storm can keep going for hours. The mesocyclone (rapidly rotating updraught) at the storm’s core carries huge amounts of water upwards so the cloud grows bigger and bigger.
During a supercell storm, other odd things can happen. Luminous, ball-shaped objects have appeared a few metres above the ground, bouncing around in a random pattern. Scientists can’t agree on the reason for this phenomenon, known as ball lightning.