Wired reports:

Firefighters in France are confronting a phenomenon never seen in the region before: fire clouds. It’s a sign of the intensity of the blazes burning—and how climate change is upping the odds that they appear.

A wave of fires has swept over France and Spain, sending hundreds of thousands fleeing. Firefighters on the frontlines are facing what a spokesperson for the French firefighter association told AFP called an “operational impossibility”—in other words, a “natural force beyond our control.”

As evidence of how out of control the wildfires in France are, look no further than the skies where the blazes have, in some cases, created their own weather. To form a fire cloud—what meteorologists call a pyrocumulonimbus or the even more metal-sounding cumulonimbus flammagenitus—you first need heat, which fires have in spades.

But just as important are dry conditions near the ground and cool, relatively moist conditions aloft in the atmosphere. As superheated smoke rises miles above the flames and into the cool atmosphere, water vapor condenses around the particles of ash to form water droplets. (Yes water vapor and water droplets are two different things.) As the air keeps rising, those water droplets eventually become ice crystals.

At this point, the smoke and water droplets have created a cloud, but unfortunately one that’s unlikely to provide much relief in the form of rain. Instead, these towering fire clouds can unleash lightning strikes that can start more fires and generate powerful downdrafts that reach the ground to fan flames further. At their worst, pyrocumulonimbus clouds can even spawn tornadoes. [Continue reading…]