SAN JOSE (NEXSTAR) – Be grateful if your morning weather forecast has never called for pyrocumulonimbus clouds. What is a pyrocumulonimbus cloud? For those of you who are rusty on your Ancient Greek, pyro refers to fire, and pyrocumulonimbus clouds are actually cloud formations created by forest fires.
Pyrocumulus clouds are similar to the cumulus clouds that humans are used to seeing. They arise when hot air transports moisture from plants, soil and air upwards, where it cools and condenses. The centers of these “pyroclouds” have strongly rising air.
It’s fairly common and a warning sign that firefighters could be exposed to irregular and dangerous conditions on the ground, from the draft of air towards the center of the fire. One such rise from California’s Creek Fire last week is possibly the largest ever recorded on US soil, according to the San Francisco Chronicle.
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Several images of the dark, menacing formation were captured by passengers and posted on social media.
Today I flew from San Jose to Las Vegas with SWA and looked out the window and saw this cloud. I found that it was a cumulonimbus flame genitus cloud, also known as a pyrocumulonimbus cloud, which is a type of cloud that forms over a source of heat, such as a heat source. B. wildfire #CreekFire pic.twitter.com/HCqyWiHpNx
– Thalia Dockery (@SweetBrown_Shug) September 6, 2020
The formations can be so damaging that NASA once dubbed them the “fire-breathing dragons of the clouds”.
“PyroCb storms send their smoke like a chimney into the Earth’s stratosphere, with persistent negative effects,” NASA explained in an overview of the phenomenon.
In some cases, the pyro clouds can reach 30,000 feet and create lightning bolts. There is evidence that pyrocumulus lightning bolts may have ignited new flames during the devastating firestorm in Australia in 2009 known as Black Friday.
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Similar to how cumulonimbus clouds produce tornadoes, these pyro clouds can create fire-generated eddies of ash, smoke, and often flames that can become destructive.
Additional destruction is the last thing California needs right now. More than three million acres have already burned this year. The peak of the state’s traditional fire season is yet to come.
The Associated Press contributed to this report.