Fire cloud on the horizon! Those columns of smoke and ash can reach up to six miles high. This summer, the Bootleg Fire in southeastern Oregon created multiple fire clouds that were visible from over 100 miles away. Meteorologists also spotted a bigger, more extreme form of fire clouds—ones that are so hot and big that they create their own weather.
Also called Pyrocumulus clouds, fire clouds look like giant, dirty-colored storm clouds. A fire cloud will sit atop a column of smoke from a wildfire. Often the top of the smoke column flattens out into the shape of an anvil.
When air over the fire becomes super-heated, it rises in a large column. As air with more moisture rises, it rushes up the smoke column into the atmosphere. The moisture condenses into droplets. That’s why “fire clouds” can look much like the thunderheads seen before a big thunderstorm. Sometimes rain does fall from the cloud. That can help put out the fire below.
But these clouds hold more than just water. Ash and particles from the fire also get swept into them.
When a pyrocumulus cloud forms over a fire, meteorologists watch carefully for its bigger, more dangerous brother, the pyrocumulonimbus cloud. NASA has called those the “fire-breathing dragon of clouds.”
Most of the clouds on the Bootleg Fire were the less-intense fire clouds. But the National Weather Service also spotted a pyrocumulonimbus cloud forming on satellite imagery.
Both types of fire clouds pose serious risks for firefighters. When one of the fire clouds on the Bootleg Fire partially collapsed, dangerous winds and embers fell on crews. Firefighters had to evacuate that part of the fire line. Thankfully, no one was injured.
In a worst-case scenario, a pyrocumulonimbus cloud could spawn a “fire tornado.” That phenomenon can spread wildfires rapidly, worsening conditions. This kind of cloud can also generate its own dry lightning and hail and create dangerous hot winds below.
U.S. Naval Research Laboratory experts say that they saw a “record number” of these fire-induced clouds in North America this summer.
In the Bible, God often uses fire as a symbol of His power. Exodus 13:21 tells how God used fire and cloud to lead the Israelites. “And the Lord went before them by day in a pillar of cloud to lead them along the way, and by night in a pillar of fire to give them light, that they might travel by day and by night.”