Sky-Protect and Hail

Hailstones exist in the lower layers of thunderclouds or within a thunder cell through sub-cooled water, which freezes to ice at the nucleuses of crystallization. This nucleus must be in the comparably lower number in this case so that the amount of water, existing for each nucleus, is adequately more to enable a quick increase. Since it pertains to clouds, with very high water content, the latent heat quantities, implemented through the phase transitions, involves a strong liability of the temperature layering within the clouds. The strong up currents, thereby generated, from completely 20 to 30 m/s are another important factor for hail formation since the freezing processes involves a continuous increase in the mass of the particle. Without an up current, the particle would drop by gravity, get removed from the cloud and thereby cannot be further increase.
It is shown that the up current is of different degree within a cloud and particle can thereby pass through a circulation. Initially, they are lifted through an up current, then they again fall in deeper air layers, absorb more water, are again pulled above and additional water freezes. This process repeats as long as it is very difficult to carry a hailstone from the up current. From the size of the hailstone, the wind force can be deduced in the internal thunder cloud, which is also used to forecast the hail diameter in the reversal.

The gradual development of the hailstone can be metered at the individual additional layers, from which there is a hailstone. The light layers thereby indicate an environment with very high water content with correspondingly rapid freezing, while the dull areas return to the lesser water contents. The cloudiness itself is thereby caused by countless small air traps. If the hailstone is finally very difficult and falls from the up current area, then this is due to the size of the hailstone and a temperature of mostly below 0°C not for melting. The size of hailstones varies widely. Thus the Hailstone-Scale of the Swiss Association differs with cantonal fire insurances of 11 intensity classes, which ranges from small hail below 0, 5 cm diameter to extensively bigger hail of above 10 cm diameter. The weight of the grain corresponding varies between 0,1 g and more than 0,5 kg. At a diameter of approx. 2cm, which corresponds to rates of fall from approx. 70 km/h, it leads to damages to cars, glass panes and camps. Smaller hail falls slowly (approx. 35 km/h), extensively bigger hail can reach the velocities by more than 150 km/h. Here you can find the current table for Size of Hail according to the classifications.

Source: Wikipedia