Hail

Hail is a very interesting phenomenon, and very impressive when it comes in the form of a hailstorm. Almost everybody has experienced it at least once. Imagine a hot summer day at the pool. It is around 30°C, but a few thunderclouds in the distance disturb the perfect picture. You can already hear a faint thunder and the clouds draw nearer. Eventually they overcast the sun, but the air temperature remains pleasantly warm. However, the first people start to pack up. And suddenly it starts. One hailstone after the other falls down from the sky until all of a sudden there are thousands, no millions of hailstones, which cover the ground with a white layer of ice.

A snowball fight between birds?

Where do these up to 10 cm (!!!!) big ice balls come from? How are they generated and why do they not fall to the ground when they are still much smaller grains?

The principle is actually very easy: Clouds suck hot air into great heights and with a speed of up to 300 km/h. It is possible that the temperature on the ground is around 30°C, but -15°C or less in the heights. These temperature differences cause hail.

Raindrops are sucked upwards by the clouds and freeze into small ice globules due to the low temperatures in these heights. Afterwards, they sag a little, gather some water, are sucked upwards again and freeze once more. This cycle is repeated again and again until the hailstone becomes too heavy and falls to the ground or doesn’t get pulled into the suction of the cloud any more. Thus, considerable hailstone sizes can be obtained.

This phenomenon may occur all of a sudden. It becomes dangerous when the hailstones get as big as pigeon eggs or even tennis balls. That hail hits the ground with such an impact that windowpanes are shattered, tiles are penetrated and even humans may be severely injured.