|A lightning, roaring thunder, heavy rain and sometimes hail (or snow) - that's a thunderstorm. One of the most impressive weather phenomena. In total, about 1600 thunderstorms occur on earth simultaneously, covering about 0.3 percent of the earths surface.|
Who doesn't know them? And who knows how they originate?
|A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth`s atmosphere known as thunder. The meteorologically-assigned cloud type associated with the thunderstorm is the cumulonimbus. Thunderstorms are usually accompanied by strong winds, heavy rain and sometimes snow, hail, or no precipitation at all.|
Lightnings result from different electrical loads in clouds and earth. That was
proven already in 1752 by the researcher and statesman Benjamin Franklin, by letting kites rise into thunderstorms. With these dangerous experiments, he also invented also the lightning rod.
In a thunderstorm, the temporary separation of electrical load develops, if ice and water particles - which load themselves differently with electrical load - are blown into different heights by strong winds within high thunderclouds. Lightning is the sudden transmission of a larger electrical load released thereby. Lightnings predominantly develop from there within thunderclouds. On the Earth, there are 40 to 50 lightning flashes per second, and 10% of these lightnings reach the ground.
Thunderclouds result from the lift of warm and damp air. The following three conditions are necessary for a thunderstorm to develop:
If a moist pack of air begins to ascend from the ground by elevation, then it cools down by around approximately 6.5 °C/km (moist adiabatic ascent) during the ascent. Starting from a certain altitude (condensation level = cloud base), water droplets originate (see cloud formation) by condensation, due to the cooling of the air. By the condensation heat (energy which is set free with the formation of water), the ascending pack of air cools down less fast than the surrounding air; thus, it stays warmer and lighter (due to the density decrease) than the surrounding air; this produces and/or even strengthens the lifting process.
Once this procedure is underway, the ascending air can reach speeds of several hundred kilometers per hour within the thundercloud. Thus, thunderclouds become often more than ten kilometers high, and up to 15 kilometers in the Tropics. Only once ascending air reaches the top margin of the troposphere, it stops to ascend further and flows off laterally. By the lateral movement of air, which is still partially mosit, the typical anvil form of a thundercloud is produced.
|Thunderstorms go through 3 phases:|
The stages are illustrated in the graphic.
Animated forecast map:
Animated radar map: shows actual precipitation.
Try to recognise the thunderstorm in the meteogram of Lille (left image). Du you see the 3 conditions causing the thunderstorm in the AIR meteogram (right image)?
Paris is also strongly affected by the thunderstorms. In the animated radar map (above, right side) you can see, how the thunderstorm front passes over Paris.