Australia bushfires: How extreme 'firestorms' make their own weather

The bushfires ravaging Australia this week have brought warnings of "catastrophic" danger. Fortunately, no lives were lost on Tuesday - when sagame conditions were at their worst.

But experts warned that events looked set to trigger the most dangerous type of bushfire - pyrocumulonimbus, often referred to as a firestorm.

These are giant, fast-moving blazes so powerful they create their own weather systems akin to thunderstorms.

And due to their ferocity, they are largely impossible to fight.

How are firestorms created?
With certain ground and atmospheric conditions, bushfires can rip through a large area with so much energy that they generate storms above them. This is a pyrocumulonimbus.

Ordinarily, bushfires are driven along by the wind but a massive blaze can carry so much power that its smoke is not pushed to the side. Instead, it forms a plume that rises up to 15km (nine miles) into the sky.

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Image caption
A large pyrocumulus cloud above the Carr fire in California in 2018
Because the plume contains heat and moisture, when it hits the stratosphere it can condense and form clouds.

"A pyrocumulonimbus is basically a thunderstorm within the plume of the fire," says Associate Prof Jason Sharples, an expert in extreme fires based at the University of New South Wales (UNSW).

What can they do?
When the storm is formed, it means the fire below หวยยี่กี will be big, fast and very dangerous.

"That means it's big enough to overcome any other conditions," says UNSW climate scientist Prof Jason Evans.