French firefighters say southwest wildfire produced France’s first pyrocumulonimbus cloud

A major wildfire in southwestern France produced a pyrocumulonimbus cloud in what a French firefighters’ representative described as the first recorded case of its kind in the country.

Lieutenant Colonel Eric Brocardi, a spokesman for the National Firefighters Federation of France, said intense heat at the centre of the fire was forcing air rapidly upwards until it met cooler air and formed a fire-generated storm cloud. A pyrocumulonimbus, also known as a cumulonimbus flammagenitus, can create its own weather conditions, including rapidly changing winds and lightning. Brocardi said the cloud was producing shifting winds that made the wildfire increasingly difficult to predict. He warned that lightning generated by the system could further feed the fire.

Such clouds can form when wildfires or volcanic eruptions heat air near the ground so intensely that it rises quickly, cools and develops into a turbulent cloud.

The source said pyrocumulonimbus clouds had most commonly been observed during major wildfires in Australia and North America.

Brocardi described the blaze as a convective fire. Unlike a more typical wildfire that advances in a broadly cone-shaped direction, he said changing winds were causing it to spread in several directions and form multiple fronts.

He said firefighters could not reliably predict the fire’s movement or confront it directly. Crews would instead have to identify weaker sections of the blaze and focus their efforts there.

Brocardi said conditions might improve after approximately three days of heavy rain or if the fire moved towards an area where it could no longer continue, such as the sea. He said firefighters had reached a stage where strategic withdrawals were necessary and the response had become largely defensive. Crews were concentrating on evacuating people, protecting critical sites and rescuing animals. Brocardi said additional personnel were available to relieve exhausted firefighters, but crews from across France could not all be sent to the region because other parts of the country also faced wildfire risks.