What makes a supercell storm so dangerous?

While all thunderstorms cause lightning, only a small proportion of the storms we see in Australia are considered severe.

So, what makes some storms more dangerous than others?

All thunderstorms require three key ingredients to form:

• An unstable atmosphere
• Low-level moisture in the atmosphere
• A trigger mechanism that causes air to rise from the surface

When these three ingredients are available in greater quantities, thunderstorms have a better chance of becoming severe.

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The Bureau of Meteorology issues severe thunderstorm warnings when there is a risk of a storm producing damaging winds, heavy rain or large hail.

However, even in this select group of dangerous thunderstorms, some are more intense than others.

The most destructive and dangerous type of thunderstorms are called supercells.

These powerful and rare storms can produce destructive winds, giant hail, intense flash flooding and sometimes tornadoes.

Unlike regular severe thunderstorms, supercells require an extra ingredient to get going: wind shear.

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Wind shear refers to a change in wind speed and direction with height as you move upwards through the atmosphere.

Of particular interest for supercell development is the rate at which wind speeds change in the lowest six kilometres of our atmosphere.

When wind shear is high enough, meaning there's a great enough change in speed and direction with height, thunderstorms can start to rotate.

This rotation is an important feature of supercell thunderstorms because it allows them to continually suck in energy from the surrounding environment without collapsing in on themselves.

Regular thunderstorms often die when the rising air within them gets too heavy from rain and hail, which causes them to collapse.

However, rotating supercells displace the rising air (updraft) from the falling rain/hail (downdraft), which allows them to grow more intense and last longer.

Regular thunderstorms usually live for tens of minutes, while supercells can go on for hours.

Their rotation also allows them to move in different directions to other storm cells surrounding them, which can make them difficult to predict ahead of time.

The best place to find information on active supercell thunderstorms are the severe thunderstorm warnings issued by the Bureau of Meteorology.

These alerts will let you know if a storm cell is capable of causing supercell impacts, including giant hail, destructive winds or tornadoes.