Described by scientists as a “fire-generated storm”, pyrocumulonimbus clouds are created in the skies of France
ByHelene WillettsMain weather presenter And Olivia Ireland
Tens of thousands of people have been evacuated from Bordeaux’s Gironde region, as France continues to battle wildfires fanned by unprecedented “pyrocumulonimbus” or clouds of fire.
Scientists sometimes describe these clouds as a fire-generated thunderstorm, because the fire itself provides the energy to build the cloud.
The enormous amount of heat generated by wildfires makes the the air above the fire rises quickly, carrying smoke, ash, and water vapor into the atmosphere.
As the air rises, it cools and the water vapor condenses into a cloud.
If the fire is strong enough and the atmosphere is unstable, this cloud can transform into a towering cumulonimbus – the same type of cloud. associated with thunderstorms.
The turbulent winds created by fire clouds can send embers in all directions, making wildfires unpredictable and more difficult to fight. Lightning strikes can also start more fires.
French firefighters blamed the fires near Bordeaux on the phenomenon, adding that it had never been observed in the country.
Across Europe, the summer months have been sweltering intense and record heatwaves with minimal rain. This means areas have become dry and vulnerable to wildfires that have broken out in France, Spain and the UK.
On Monday, the Gironde prefecture indicated that the situation had remained “generally stable” overnight.
But efforts to fight the fire could become even more complicated with a new heatwave forecast later this week, with temperatures of up to 40C (104F) forecast in France this week.
The Gironde wildfire will likely burn “for several weeks” and could take months to be completely extinguished, a senior official involved in the response has warned.
French firefighters’ fire may have caused unprecedented pyrocumulonimbus cloud
Pyrocumulonimbus clouds are more likely when conditions are extremely dangerous such as high temperatures, strong winds, and low humidity.
Scientists predict that climate change will likely increase the risks of such events.
Smoke rises into the sky following forest fires in Saint-Jean-d’Illac, France.
Although once considered a fairly rare event, a similar example was seen during the 2019-2020 Black Summer bushfires in Australia, which created extreme “firestorms” that created its own climate.
The event was one of most intense and catastrophic fire seasons for the country, with at least 33 people killed – including four firefighters – and more than 11 million hectares (110,000 km2 or 27.2 million acres) of bushland, forests and parks across Australia burned.
Firefighters in New South Wales reported that the embers of the storm landed 30 km in front of the front, three times further than the usual distance.
At the time, NASA described the pyrocumulonimbus as “the fire-breathing cloud dragonexternal” as they channeled smoke like a chimney into the Earth’s atmosphere while throwing lightning, wind and rain.
A pyrocumulonimbus cloud generated by the Orroral Valley bushfire south of the Australian capital Canberra in January 2020
Similarly, in California, during the summer of 2021, intense fires raging across the western United States generated pyrocumulonimbus clouds.
Clouds of smoke were 1 mile tall and rising above the fire in California and neighboring states.
California fire officials said that at the time of the season, more than 7,300 wildfires had burned 1 million hectares (2.5 million acres) and at least three firefighters had been killed.
Smoke rises in Markleeville, California during the July 2021 wildfires