Fire clouds: The ominous new threat looming over wildfires in France

Firefighters battling devastating fires in France have had to contend with a new threat: immense fire clouds that create their own wind and even lightning that can spark fresh blazes.

Fire clouds - or pyrocumulonimbus flammagenitus clouds - are towering thunderstorms created by an extreme heat source, and they can exacerbate already dangerous conditions.

Pyrocumulonimbus clouds can form above volcanic eruptions, where super-heated air rapidly rises into the atmosphere - and they have also been created by large-scale bushfires in the United States and Australia.

But the phenomenon is new to France and is considered yet another consequence of human-caused climate change, according to French researcher Jean-Baptiste Filippi, who studies wildfires.

A fire cloud is formed from a rapidly rising convective current that can reach the stratosphere, and can produce rain, hail, lightning and extreme ground winds - and sometimes tornadoes.

The combined effects of these phenomena can greatly increase the fires that caused the cloud. In some cases, resulting rain can also extinguish the fire.

Filippi said France needed to quickly learn about the dangers posed by fire clouds. “It is a common phenomenon in Portugal, California and Australia, where firefighters are more used to them,” he said.

“In France, pyrocumulonimbus clouds are quite new. Therefore, we need to learn how to manage fires that creates their own wind - this is something relatively new.”

Filippi said there was no doubt climate change was to blame for the arrival of fire clouds in France.

“A consequence of global warming is more frequent heatwaves. While thunderstorms are common in the region of this fire, thunderstorm conditions after three successive heatwaves is a new combination.”

He said the biggest problem was the unpredictable nature of a fire cloud.

“Weather services can predict thunderstorms. But because these storms are located directly above a fire, we would need to know the fire’s exact location in advance. That’s impossible.

“The fire in France’s southwest Gironde region started with northerly winds, then westerly, then southerly, then easterly, then back again to the south, then the west.

“On top of that, there is this potential energy in the atmosphere which meant that, locally, the convection column sucked up the embers and carried the fire further afield.

“The local conditions became catastrophic and the rate of the fire’s spread was staggering.”

- AFP