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Pyrocumulus Clouds, Dry Lightning, and Fire Tornadoes

Don Wyeth

Pyrocumulus Clouds, Dry Lightning, and Fire Tornadoes

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3 mins
July 28, 2021

Between 1970 and 1978, I made my home in a little forest community just east of Azalea, Oregon, located in the southcentral Umpqua National Forest. I remember it being a beautiful area with stately Douglas fir trees and Madrone. Normally it rained from fall through the spring with little or no snow. The first year I was able to go out in my shirt sleeves to cut my Christmas tree.  I had purchased an old country schoolhouse on Cow Creek Road (cow elk), which I remodeled as best I could, considering my economic situation at the time. All in all, it was a happy time in my life. When I wasn't teaching school, I worked in the Roseburg plywood mill and in the woods with a friend of mine surveying and cutting trails. Having had this experience in southern Oregon, I still feel connected to the area. So, I was grieved to find out that a large swath of the forest is now burning out of control.

The weather in southern Oregon is very different now from what it was when I lived there. I don't remember ever having a record heat recorded the whole time I spent on Cow Creek. However, “…[t]his year has seen a brutally hot, dry summer in the Western U.S., with hundreds of heat records broken amid an unprecedented drought that has created a tinderbox for ferocious wildfires.” Forest fires that we are seeing now, as compared to the ones 40 years ago, seem to be on steroids. Is it is pretty much confirmed that this change is due in part to weather events being caused by climate change. These fires carry with them the added threat of altering the weather in the areas where they occur. There are three major phenomena that are associated with these mega fires that make them so dangerous. Pyrocumulus clouds, dry lightning, and fire tornadoes.

Pyrocumulus clouds… look like giant, dirty-colored thunderheads that sit atop a massive column of smoke from a wildfire. Often the top of the smoke column flattens into the shape of an anvil.” These are caused when the air above the fire becomes super-heated and rises into a huge column. This column, which contains high amounts of moisture, can ascend as high up as 5 miles. When the conditions are right, these can morph into a more dangerous form called Pyrocumulusnimbus clouds. They are a source of high winds and lightning. “…NASA has called these clouds the “fire-breathing dragon of clouds," in part because they can ravage tens of thousands of acres.”

Then, there is dry lightning. “…according to the National Severe Storms Laboratory, dry lightning is lightning that hits the ground without rainfall nearby.” As the humid air created by the fire ascends, it feeds a thunderstorm, which causes rain. However, the intensely hot surface temperatures created by the fire cause the water droplets to evaporate before they hit the ground. This does not prevent the lightning from happening though. This kind of dry lightning combined with a tinder dry forest floor spreads fire more rapidly than it would otherwise spread.

The third category, the fire tornado, also known as a fire whirl, is one of the most lethal phenomenon which fire crews have to contend with. “A fire whirl is a "spinning vortex column of ascending hot air and gases rising from a fire and carrying aloft smoke, debris, and flame, according to the Bureau of Land Management's Glossary of Wildland Fire Terminology.” The size of these monsters can measure from 1 to 500 feet in diameter! These whirls are created in much the same way as a regular tornado. They happen when cooler air flows in to take the place of hot air, creating a rotation. Fire tornadoes, which are equivalent to a category two or three regular tornado, are capable of spreading embers and sparks for very large distances, which further increases the fire’s intensity.

According to the EPA, wildfires like the ones in Oregon and the rest of the western states, are contributing significantly to the degradation of air quality in the region and the rest of the country. There are health issues associated with this kind of contamination. In human beings and other mammals. the symptoms can range from eye and respiratory irritation all the way to “…reduced lung function, bronchitis, exacerbation of asthma and heart failure, and premature death.” epa.gov. “There are currently 80 large wildfires raging in 13 states across the US, burning more than 1 million acres, mostly in western states, according to the National Interagency Fire Center (NIFC).” cnn.org. In my view, those continuing to deny climate change and its relation to increased fire danger are not only foolish but border on suicidal ideation.


This article was orginally reported by
Don Wyeth

Passionate and intelligent columnist from Madison, WI.

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