Nearly a week into devastating wildfires in France, officials said that firefighters had encountered a phenomenon that many of them had not seen before: a pyrocumulonimbus, or “fire cloud.”
These large thunderclouds, also known as pyroCbs, are created by intense heat from large fires or volcanic eruptions, which in turn can spark more fires. In other words, it is a fire-fueled thunderstorm that does not bring rain.
One pyrocumulonimbus generated more blazes over the weekend in one of the hardest-hit areas of France, Marc Vermeulen, the director of fire and emergency services in the Gironde region, said at a news briefing on Sunday.
“While this type of fire occurs regularly in Canada and Australia, it is unprecedented in France,” Lt. Col. Eric Brocardi, a spokesman for the National Firefighters Federation of France, told Agence France-Presse.
“The fire became extremely virulent and unpredictable again generating its own wind and spreading erratically toward the Bordeaux metropolitan area,” Laurent Nuñez, France’s interior minister, also said on social media.
Wildfires are so hot they can sometimes create their own weather systems. The smoke from the fires acts as a plume of heat rising into the atmosphere, according to Britain’s Royal Meteorological Society.
The hot air rises, which causes it to cool and expand. Once it is cooled sufficiently, the cloud’s vapor condenses onto the ash from the fire and forms a gray or brown cloud that can then develop into a pyrocumulonimbus (pyro means “fire” in Greek). Once it has formed, the storm cloud can carry embers and start new blazes elsewhere.
In the Gironde region, 103,000 acres have burned, according to officials, and 220,000 people have been asked to evacuate from Gironde and the neighboring Landes region.
The pyrocumulonimbus phenomenon presents extreme challenges for firefighters.
“These fire-generated clouds are linked to extreme fire behavior that impedes firefighting efforts and can devastate communities,” according to NASA, which emphasized the need to better understand the clouds “given the ongoing and projected increases in fire activity and severity.”
Ephrat Livni contributed reporting.
