In New Zealand thunderstorms and lightning are some of the most exciting and dramatic weather events we see. It is estimated that about 2000 thunderstorms are happening across the world at any one time. Thunderstorms have their importance in the world, bringing regions much needed rainfall, however they can also be destructive forces and a risk to life. In addition to lightning, thunderstorms can also bring heavy rain, hail, tornadoes, and waterspouts.
Most thunderstorms occur from massively tall cumulonimbus clouds. The sun warms moist air near the earth’s surface and makes it rise. As this air moves upwards it cools and can condense to form cumulus clouds. The small, white fluffy cumulus clouds can group together and form one larger cumulonimbus cloud if there is enough rising warm air. If tall enough to reach the cooler air of the stratosphere, strong winds may widen the top of the cumulonimbus cloud. This may have the appearance of a top-heavy, flattened, anvil shape and is a good indicator that a thunderstorm is on its way.
The way thunderstorms form mean they are more common in the afternoons of tropical regions where there is more moist, warm air and more heat to make it rise. Most parts of the world have thunderstorms, especially mountainous areas, which help form cumulonimbus clouds with increased uplift of air. Only hot, dry deserts and extremely cold polar regions rarely see thunderstorms.
What makes thunder?
Thunder is the rumbling or crack of sound that can usually be heard from the sky during a storm. Thunder is caused because lightning heats up the air, to about 30 000ºC, causing it to expand quickly. The rumbling occurs as the sound passes through atmospheric layers at different temperatures.
How far away is a thunderstorm?
Lightning along Darwin’s Nightcliff Foreshore, NT, Australia