French firefighters are facing a new challenge in their battle against large-scale wildfires: the emergence of a pyrocumulonimbus cloud, commonly referred to as a “fire cloud,” which has developed during the ongoing disaster that has persisted for nearly a week.
These large storm clouds, known as pyroCb, form from the intense heat generated by massive fires or volcanic eruptions and can lead to new fire outbreaks. Essentially, they are thunderstorms fueled by fire that do not produce typical rainfall.
According to Marc Vermeulen, director of fire and rescue services in the Gironde region, one such pyrocumulonimbus cloud triggered new fire outbreaks over the weekend in one of the areas hardest hit by the wildfires in France.
“Although this type of fire regularly occurs in Canada and Australia, in France it is an unprecedented phenomenon,” said Lieutenant Colonel Eric Brocardi, spokesman for the National Federation of Firefighters of France, in an interview with the Agence France-Presse news agency. France’s Interior Minister Laurent Nuñez also noted on social media that the fire “has again become extremely intense and unpredictable, generating its own wind and spreading chaotically towards the metropolitan area of Bordeaux.”
How fire clouds form
According to the British Royal Meteorological Society, wildfires can be so intense that they sometimes create their own weather phenomena. Smoke from the fire acts as a stream of hot air rising into the atmosphere. The hot air cools and expands. After sufficient cooling, water vapor in the cloud condenses on ash particles, forming a gray or brown cloud that can eventually develop into a pyrocumulonimbus cloud (“pyro” means “fire” in Greek).
Once formed, such a storm cloud can carry embers and burning debris, igniting new fires in other locations.
Scale of destruction and challenges for firefighters
According to official data, in the Gironde region, 103,000 acres (about 41,682 hectares) have burned. 220,000 people have been asked to evacuate from Gironde and the neighboring region of Landes.
Pyrocumulonimbus clouds pose extreme challenges for firefighters. According to NASA, these fire-induced clouds “are associated with extreme fire behavior that hinders firefighting efforts and can devastate communities.” NASA emphasized the need for a better understanding of this phenomenon “given the current and expected increase in the number and intensity of fires.”
Source: NYT
