Thunderstorms
Yesterday’s thunderstorm is a timely reminder we are now coming into the season of thunderstorms. Here in Maleny we average 30 thunderstorms a year of which ten are usually with hail.
First indication we get of a thunderstorm approaching is a change in sky to stratus and cumulonimbus. The sound of distant claps of thunder is heard. Should fork lightning be observed then its distance away can be calculated by counting in seconds from the instant a lightning is seen to when the thunder is heard. Divide by three and the answer is in Kilometres.
The thunderstorm activity is the result of unstable weather when hot moist low level air is trapped by a temperature inversion from the cold dry air above. In such a scenario the low level air becomes agitated and driven by hot winds desperately tries to break through the barrier and when it does a towering storm Cumulonimbus cloud develops, rising to great heights.
Hail is a spectacular by-product of thunderstorms. It begins life as a frozen droplet of water that is carried aloft in the updraft area of a thunderstorm. Sometimes as it falls back to earth it will be trapped in the updraft a second time before falling again. This can happen several times resulting in another layer of ice being deposited on the growing hailstone. A hailstone cut in two reveals a ring-like structure like an onion. As many as 25 rings have been counted. Sometimes dust, pollen and small insects can be seen when the hail has melted.
Two well recorded episodes of orange-sized hail in Sydney were on 1st January 1947 and 14 April 1990 when there was tremendous damage to vehicles and houses. Permanent evidence of the size of hailstones was made by a Sydney dentist who made a dental impression of two hailstones and used these moulds to produce replicas of them. They were similar in size to a tennis ball.
The earliest mention of hail that I could find is in the Bible Old Testament’s Book of Joshua describing the discomfort of Canaanites armies during a hailstorm, and I quote:-
“… the Lord cast down large hailstones from the sky on the Canaanites, and more of them died from the hailstones than were killed by the swords of the Israelites…”
Heard this one?
Patient: Doctor, can I have a second opinion?
Doctor: Come back tomorrow!