Fire clouds or pyrocumulonimbus observed in France for the first time
For the first time, dangerous 'fire clouds' or pyrocumulonimbus have been observed during wildfires in France, creating their own wind and lightning that can ignite new blazes.
According to researcher Jean-Baptiste Filippi, this phenomenon is another consequence of human-caused climate change. Fire clouds, or pyrocumulonimbus, form when a column of hot air rises above a large wildfire. It starts as a small white cumulus cloud as water vapor condenses. Once the surrounding air becomes hot enough, it develops into a towering anvil-shaped cumulonimbus, containing thousands of tonnes of suspended water. Updrafts can exceed 150 km/h. Rain falls but evaporates before reaching the ground, yet it cools the atmosphere, creating strong downdrafts.
While common in Portugal, California, and Australia, fire clouds are new to France. In Portugal, they were rare until the deadly 2017 fires in Pedrogao Grande. First observed briefly in France in 2022 in Landiras, south of Bordeaux, they highlight the need for firefighters to learn how to manage fires that create their own wind. Filippi says that more frequent heatwaves due to global warming are to blame. Although thunderstorms are typical in the region, three consecutive heatwaves combined with fire conditions create a new mix.
The biggest challenge is their unpredictability. Weather services can forecast thunderstorms but not the exact location of the fire. The Gironde fire in southwest France began with northerly winds, then shifted to westerly, southerly, easterly, and back. Additionally, atmospheric potential energy caused the convection column to suck up embers and spread fire further. Local conditions became catastrophic, with staggering rates of fire spread.
