2023-06-21 03:30:35
Christian Stefan from GeoSphere Austria said regarding the typical thunderclouds: “These are a cumulonimbus, the most powerful clouds that reach from the lowest level up to the tropopause. They extend from 10 to 15 kilometers in height.” Lightning equalizes the tension between the clouds and the earth, but not only that: “There are also many lightning bolts that equalize the tension within a cloud. That is visible as a spark.”
Charges are separated and cause sparks
Thunderclouds contain supercooled cloud droplets and ice crystals that are charged differently. According to Stefan, the charge is separated by this thunderstorm mechanism. If the voltage differences are large enough, a spark is created, a lightning bolt that balances out the differences: “A lot of current flows and the air in the lightning channel heats up very quickly.” Expansion of the air and it’s like an explosion, like a wave traveling at the speed of sound. This is audible as thunder.”
Cumulonimbus
Thunder calculates distance
On the one hand, thunder is the acoustic indicator of a thunderstorm, but it also reveals other details regarding the thunderstorm: “You can calculate the time difference between lightning and thunder. You can see lightning immediately, it spreads at the speed of light, thunder at the speed of sound. If you count to three, the thunderstorm is regarding a kilometer away,” says Stefan.
Thunderstorms are often short and violent, but not always: “There are also long-lasting thunderstorms, either they are super cells, they are huge thunderstorm cells over 15 to 20 kilometers in extent. This is rather the exception for us. Or there are multi-cell thunderstorms, this complex then has a lifespan of several hours. A single thunderstorm cell has a lifespan of half an hour or an hour.”
Stratocummulus
Hailstones are carried by the updraft
Unpleasant companions of a thunderstorm are often hailstones: “Basically, a thundercloud contains sleet grains that collide with water droplets and can accumulate. In a thunderstorm we have large areas of updraft, that is wind speeds of 50 to 100 km/h, which are directed upwards and which keep water and sleet particles in the air.”
The particles have to be kept in the air long enough for the hail to form: “Due to the strong updraft, they stay in the air, grow ever stronger, get bigger and bigger until they are so big that the updraft tube can no longer carry them can. Then they fall down. If they are large enough, they fall as hail, if they are smaller they melt on the way and form large raindrops.” According to Stefan, it depends on where the zero-degree line is in the cloud and how strong the updraft area is.
Castilian Wolke
Exact prediction not possible
There are clear indications of thunderstorms for those who are attentive: “For example, there is the Altus Cumulus Castellanus cloud. They look like the towering battlements of a castle, pointing to unstable air stratification. If you see that in the morning, you can assume that there will be thunderstorms in the evening because the atmosphere is very unstable.”
However, it is not possible to precisely predict where there will be thunderstorms: “There are many random processes that play a role in where a cloud is formed. Once a thundercloud has formed, it can be predicted for the next few hours. But to say in the morning that there will be a thunderstorm here or there is practically impossible.”
Heavy rain, hail and thunderstorms
Local thunderstorms are forecast for Carinthia on Wednesday. There is a risk of larger hail, strong gusts of wind and torrential rain, the temperatures are between 28 and 34 degrees. The risk of thunderstorms is expected to be lowest in the central and eastern Klagenfurt basin. On Friday there will be a low with some violent thunderstorms, the heat will be broken. But it stays muggy up to 29 degrees.
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