Incoming!

Hail is a form of solid precipitation. It consists of balls or irregular lumps of ice, each of which is called a hailstone.

A single hailstone has a diameter of 5 mm or more and can grow to 15 cm, weighing more than 0.5kg (!).

Hail is composed of transparent ice or layers of transparent and translucent ice, at least 1mm thick, which are deposited on the hailstone as it travels through cumulonimbus cloud. It forms in these strong thunderstorm clouds, beginning as water droplets that rise up through the cloud on intense updrafts.

As the hailstone passes through the cloud it collects water droplets that appear as a translucent layer, or water vapour that appears as a layer of opaque white ice. When a hailstone is dissected, it has a layered appearance much like an onion.

As the hailstone grows it releases latent heat, keeping it's exterior surface in a liquid phase, making it 'sticky'. A single hailstone may grow by collision with other hailstones, forming a larger, irregularly shaped entity.

Once the mass of the hailstone becomes too heavy for the updraft to support, it falls back down through the cloud, continuing to grow, until it leaves the cloud.

The things you have time to look up when the weather forces you to stay indoors! The hailstorm we had today was preceded by one almighty flash of lightening and a deafening clap of thunder!