Hail is the maximum expression of atmospheric instability , and this usually occurs in the afternoons, when the gradual process of warming the soil culminates. Its formation originates with the presence of a solid particle, dragged by strong ascending winds within the cloud, to which water particles are attached. As they rise, the particles freeze, and hail balls can form between five and fifty millimeters in diameter , and even more.
Hail also occurs in intense storms and in clouds called cumulonimbus clouds . Although this type of cloud is more frequent during the afternoon and last hours of the day, it needs daytime heat and very cold air in the upper-middle part of the troposphere – layer of the atmosphere that is in contact with the surface of the Earth – so that the natural chimney is formed that drives up the convective currents of hot and humid air and the subsequent vertical development of this type of clouds.
In short, it is rare that there are strong night hailstorms , due to the cooling of the soil, although there may be situations of exceptionally cold air in the upper part, which do not require excessively hot air at low levels to trigger the process that gives rise to the formation of hail , and that it reaches the sufficient size to reach the ground as such. In addition, at night the hail goes unnoticed, but there are antecedents, especially in the case of very strong storms, of night hail.
