Thunderstorms
Heavy rain, dark black clouds and lightning are evidence of a thunderstorm. Thunderstorms are not nearly as large or as strong as hurricanes, but they can be damaging, particularly if large hailstones fall out from their clouds. Thunderclouds are known scientifically as cumulonimbus clouds.
Thunderstorms are more common in summer because they need a lot of energy to form. The energy comes from the heating of the ground and the surface air by the Sun. If this heating is strong enough, air heated near the ground will rise up a long way into the atmosphere because it is lighter than air around it, a bit like a hot air balloon. Warmer air is lighter than colder air. As the air rises up it becomes colder. Moisture in the air begins to condense out as clouds, in the same way as fog forms on a calm cool night. In thunderclouds however, the energy is much greater, and the currents of air are strong enough to split apart the raindrops that are forming. This builds up an electric charge, which when released is seen as lightning. The sound of thunder is effect of the lightning strike on the surrounding air.
When the rain or hail begins to fall from a thundercloud, it is usually very heavy, but generally lasts for no more than 30 minutes. Sometimes however, the death of one thunderstorm may lead to the development of another, and the bad weather may continue for several hours.
| Thunderstorm from space |
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