France hit by rare fire thunderstorms

Firefighters in southwest France are grappling for the first time with a wildfire so intense that it is generating a dangerous phenomenon called pyrocumulonimbus – thunderclouds that can spark new blazes

HOW PYROCUMULONIMBUS FORM

Heat from wildfire causes air above to rise rapidly, carrying smoke, ash and water vapour high into atmosphere

As air rises, it cools and water vapour condenses into clouds

Fully mature pyrocumulonimbus, or “fire clouds”, develop, sometimes reaching stratosphere

Fire clouds can generate own lightning, sparking new fires

This may also lead to intense, localised rainfall

With erratic winds reaching up to 160km/h, intense updrafts can fuel wildfire spread and pose risks to aviation

Stratosphere base: 8-15km above sea level

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Sources: NASA, Australian Bureau of Meteorology
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