Pyrocumulonimbus cloud in Northern California in July 2014. Source: NASA Earth Observatory
From California to the Arctic, wildfires have been in the headlines for months now; their effects have been nothing short of far-reaching, as their smoky plumes have transported smoke to areas that are hundreds, if not thousands away from their sources. Such has been the case in Alaska, where significantly above-average temperatures have resulted in several uncontained wildfires. Their smoke plumes soon spread and et transported by atmospheric wind motions up into higher levels of the troposphere. In many instances, these conditions result in the development of a unique cloud type referred to as pyrocumulus clouds.
Wildfire in the Arctic Circle. Source: New York Post
These cloud types are essentially produced in much the same way that all other cloud types are; as the air around the wildfire heats up, its lighter density than the surrounding air allows for it to rise, bringing with it both the particles from the smoke and any water vapor that gets attached to said particles at the surface level. Once they condense, these particles and the water vapor that clung to them become what we refer to as a pyrocumulus cloud.
Pyrocumulus developing in Northern California. Sourvce: NASA Earth Observatory
As a wildfire continues to expand, so too does the area of greatest surface heating. As a result, those same vertical motions that helped to produce the initial pyrocumulus cloud will increase in intensity, resulting in more particles and water vapor making up and into higher levels of the troposphere. In some instances, these clouds can reach heights of up to 8 kilometers (5 miles), resulting in the development of pyrocumulonimbus clouds. Essentially, a wildfire of a strong enough size and magnitude can produce localized thunderstorms. Should these storms develop with low enough water vapor content, the end result can be virga and lightning strikes that can actually spark new fires in the surrounding areas. Likewise, if there is enough moisture content in the pyrcumulonimbus cloud, then the end-result can be rain that can kill off some, or all, of the wildfire that helped to produce it in the first place.
Wildfire in Shasta County, California on August 1st, 2014. Source: @Weather1225
In extremely rare instances, wildfires can even produce supercell thunderstorms! This was witnessed back in May 2018 over the Texas Panhandle when a substantially strong wildfire produced strong enough updrafts for a pyrocumulonimbus cloud to develop. This cloud just so happened to develop on a day with substantial low-level wind shear, low-level moisture, and instability supercell development. All that was needed was a source of lift, which in this instance came in the form of a wildfire. As a result, the cloud soon moved away from its source and evolved into a unique pyrosupercell just southeast of Amarillo, Texas.
Pyrosupercell thuderstorm just southeast of Amarillo, Texas, in May 2018. Source: Silver Lining Tours
Pyrocumulonimbus clouds are some of the most interesting cloud types out there; it can be said that these beasts are born out of the ashes, and as they evolve they can produce some of the most phenomenal and breathtaking sights on Earth. Indeed, these clouds are just one part of the dynamics and characteristics of a given wildfire, but their unique properties and evolution during such conditions are all worth the exploration.
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©2019 Meteorologist Gerardo Diaz Jr.