Add fire-induced storms to the list of intense consequences from Australia's bushfires, as a wildfire season that began in October persists. Caused by several years of extremely dry conditions and hot summer temperatures (both exacerbated by climate change), occasional rain isn't enough to douse these flames — and won't, until autumn comes to the continent.
Thousands of people have evacuated from their homes along the eastern coast south of Sydney, 24 have died, and animals are racing to get out of harm's way. An area roughly the size of Denmark has burned, The New York Times estimates.
The devastation is linked to the intensity of the fires, which are not just destroying bushlands and homes, but also causing local weather phenomena that have not been witnessed by humans at this scale.
In March 2016, this famous 'Hiroshima strike' photo was finally corrected. It shows a pyrocumulonimbus cloud caused by the massive fires several hours after the atomic bomb was dropped, not the bomb explosion itself. It was misidentified as such for decades. (Photo: U.S. military [public domain]/Wikimedia Commons)
One of the most visually dramatic fire creations are pyrocumulonimbus (sometimes abbreviated as pyroCb) clouds. They're formed by a massive source of heat — either a fire or sometimes a volcano, and NASA describes them as the "fire-breathing dragon of clouds."
"It's when a fire gets so big, and there's so much heat released, that the airmass from the fire rises vertically into the atmosphere, but really really deep, unlike most smoke plumes," Craig Clements, director of the San Jose State University Weather Research Lab, explains in the video below. "To have so many at one time is unique. This is probably the largest outbreak of pyrocumulonimbus on Earth," says Clements.
Because the smoke punches so deep into the upper atmosphere, hitting as high as the tropopause (the barrier between the lower atmosphere and stratosphere), it can easily be seen from space. That smoke also travels, affecting those who live far from the fires — Sydney, Canberra and Melbourne have all had multiple days of unhealthy and hazardous breathing conditions.
But the smoke has traveled much farther than that. Using satellite data, NASA scientists have tracked the smoke's movement and found that it has actually circumnavigated the Earth. In the image below, the black circle shows the smoke returning to Australia after having traveled around the world.
In addition, pyroCb clouds also cause massive thunderstorms, including lightning, which can cause more fires. These storms also create intense downdrafts as hot air pushes up into the atmosphere, causing fire tornadoes, and also causes embers from the fire to travel, creating yet more fires. These "ember attacks" are dangerous for any person or animal exposed to them — imagine small pieces of woody debris on fire and flying through the air.
During a recent ember attack, firefighters were able to take cover in their truck, and they told NBC News what it was like: "Everything was alight, both sides of the truck, the top — everything. It was like being in an oven."
Editor's note: This story has been updated with new information since it was written in January 2020.