A monster wildfire in southwest France has become so powerful that its smoke column generated a thunderstorm, producing lightning that ignited new fires. The blaze near Saumos in the Gironde department now covers 162 square miles. It started on July 22 and has forced 240 homes to be abandoned and 220,000 people evacuated.
Pyrocumulonimbus phenomenon
Firefighters in France encountered a pyrocumulonimbus (pyroCb) for the first time, according to the country's national firefighters federation. The departmental fire and rescue service reported that the fire spawned the storm cloud just two days after ignition, with heat and smoke rising into a black, electrified thundercloud.
Theodore Giannaros, a fire meteorologist at the National Observatory of Athens, explained: “Imagine a campfire so large and hot that the smoke rising off it turns into a storm-like cloud. That is a pyroCb — a storm cloud born from the intense heat that a wildfire produces.”
Rare in Europe
Pyrocumulonimbus clouds are rare in Europe, typically occurring in more extreme conditions in North America and Australia. Portugal recorded one during its deadly 2017 fire season. The phenomenon requires very hot, dry air near the ground with cooler, moister air above. Hot air loaded with smoke and moisture rises rapidly, and as it cools, water vapor condenses around ash particles. Above freezing, ice crystals form and generate electrical charges, similar to an ordinary thunderstorm.
Giannaros added: “It’s a feedback loop, not a one-way effect. Once it forms, the cloud becomes its own weather system, sitting on top of the fire and making it harder to predict.” The systems can also produce fire whirls, which he described as a dust devil made of fire and heat.
Worsening crisis
About 300,000 people have been displaced in the past week alone. French President Emmanuel Macron said the crisis is the worst since World War Two. During a visit to the fire and rescue operational centre in Bordeaux, he called the Gironde blaze “unprecedented” and warned: “The weeks ahead will be difficult and we must hold on.” Fires are expected to worsen with a looming 40°C heatwave, increasing the risk of new blazes and complicating efforts against existing ones.
