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PORTLAND, Ore. (AP) – Smoke and heat from a massive wildfire in southeastern Oregon creates giant “clouds of fire” above the blaze – dangerous columns of smoke and ash can reach up to 10 kilometers in the sky and are visible from over 100 miles (160 kilometers) away.
Authorities put these clouds at the top of the list of extreme fire behavior they see on Bootleg Fire, the largest wildfire in the United States. Hell grew to about 75 square miles (194 square kilometers) more than the size of New York City on Friday and was raging in a part of the western United States that was experiencing a historic drought.
The blaze was so dangerous Thursday night and Friday that authorities withdrew teams. Meteorologists this week also spotted a larger and more extreme form of fire clouds – those that can create their own weather, including “fire tornadoes.”
The extreme fire behavior, including the formation of more fire clouds, is expected to persist on Friday and worsen through the weekend.
WHAT ARE “FIRE CLOUDS?” “
Pyrocumulus clouds – literally translated as “clouds of fire” – look like giant, dirty-colored thunder heads that sit atop a huge column of smoke rising from a fire forest. Often the top of the smoke column flattens out into the shape of an anvil.
In Oregon, fire departments say clouds form between 3 p.m. and 5 p.m. each day as the sun penetrates the layer of smoke and warms the ground below, creating an updraft of air. hot. On this fire, the crews see the biggest and most dangerous clouds over a part of the wilderness made up mostly of dead trees, which burn instantly and with great heat.
For four consecutive days, the Bootleg Fire generated several clouds of fire that rise nearly 6 miles (10 kilometers) into the atmosphere and are “easily visible from 100 to 120 air miles” (160 to 193 kilometers), the authorities said on Friday. .
The conditions creating the clouds are expected to worsen over the weekend.
WHAT IS THE SCIENCE BEHIND THESE CLOUDS?
When the air above the fire becomes superheated, it rises in a large column. As the air with more humidity rises, it rushes up the column of smoke into the atmosphere, and the moisture condenses into droplets. This is what creates the “clouds of fire” which closely resemble thunderstorms seen before a large thunderstorm.
These clouds, however, contain more than water. Ashes and fire particles are also swept away there, giving them a dark gray and ominous appearance.
IS THERE SOMETHING EVEN MORE DANGEROUS THAN A “CLOUD OF FIRE”?
Yes. When a pyrocumulus cloud forms over a fire, meteorologists begin to watch closely its big brother, the pyrocumulonimbus cloud.
NASA has called the latter the “fire-breathing cloud dragon” because they are so hot and large that they create their own climate.
In the worst-case scenario, fire crews on the ground could see one of the monster clouds spawn a “tornado of fire,” generate its own dry lightning and hail – but no rain – and create storms. dangerous hot winds below. They can also send smoke column particles up to 10 miles above the Earth’s surface.
So far, most clouds on the Bootleg Fire have been less intense fire clouds, but the National Weather Service spotted a pyrocumulonimbus cloud forming over what it called on Wednesday. “terrifying” satellite images.
“Please send positive thoughts and best wishes to the firefighters. … It’s a tough time for them right now, ”the weather service said in a tweet.
ARE THESE CLOUDS DANGEROUS?
Both types of fire clouds pose serious hazards to firefighters.
Several pyrocumulus clouds were spotted for four consecutive days, and one of them on the southern flank of the blaze partially collapsed on Thursday, causing dangerous winds and embers to fall over the mountains. crews.
This resulted in the emergency evacuation of all firefighters and earth removal equipment from that part of the fire line. Authorities say no injuries have been reported.
“We expect these same conditions to develop today and worsen even until the weekend,” Fire Department spokeswoman Holly Krake said on Friday.
WHERE ELSE WERE THESE CLOUDS FORMED?
These types of fire-induced clouds are becoming more common as climate change lengthens and intensifies the wildfire season in the western United States and other places, including Australia.
Experts from the US Naval Research Laboratory said in a press release Friday that they were seeing a “record number” of these fire-induced clouds in North America this summer, including in Oregon, Montana and British Columbia.
For example, a forest fire in British Columbia last month, which razed an entire city also generated a cloud of pyrocumulonimbus.
The fires in California in 2020 and in previous years created several pyrocumulus clouds, with the Creek Fire in the Fresno area generating a powerful pyrocumulonimbus cloud last fall.
The siege of the bushfires in Australia in January 2020 also produced pyrocumulonimbus clouds that threatened to produce a tornado of fire.
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