Stop Press! "Every hail stone was the size of four inches in circumference. Each went two inches into the earth, and those that fell on water went right to the bottom like a natural stone. Some from the shower struck a woman on the head, and even under her hood she was severely wounded. A hen was killed in Ballykilmurry."
But perhaps the need for urgency is gone. This fatal hailstorm did not take place today or yesterday, but at Castletown, near Ballycumber, Co Offaly, in March 1635, and is described by a contemporary chronicler.
It is remarkable, however, not just for the hen's demise, but because in Ireland hailstones above a centimetre or two in diameter are very rare. But we must take him at his word; a hailstone of this size, even here, is not impossible. As a general rule, not even the very largest raindrops measure more than about a quarter of an inch. As the drops fall through the turbulent air they collide and coalesce with others to form bigger ones; but these larger raindrops oscillate and change their shapes, and in due course the deformations cause the larger drops to rupture in their turn, and form a multiplicity of smaller ones. The bigger the drop, the greater are the chances of its breaking up - and hence the limitation on their size.
But hailstones, being solid, have no such aerodynamic limits to their magnitude. In their case the controlling factors are the speed and longevity of the powerful updrafts in which they have their origins.
Large hailstones fall from deep cumulonimbus clouds, which form when warming near the ground makes the air buoyant in the lower layers, and causes the atmosphere to bubble upwards like boiling water in a saucepan.
A hailstone begins its life as a small particle of ice; as it moves within the cloud, it encounters tiny drops of "super-cooled" water - water still liquid below the freezing point - and these droplets freeze on impact with the hailstone to make it larger. An individual lump of hail may make several trips up and down the cloud, accumulating an extra layer of ice on each journey.
As many as 25 layers of ice have been counted on a single hailstone, each encapsulating the one inside after the manner of an onion. The more powerful the vertical currents in the cloud, the longer a hailstone will remain suspended in the air, growing all the time. But eventually it becomes so heavy that it must succumb to gravity, and fall to earth - as one did on that unlucky hen near Ballycumber.