The science behind the 'thunderclouds' forming over Oregon's Bootleg Fire Often associated with volcanoes, scientists are now noticing clusters of PyroCbs in wildfires. Here's what to know about these smoke-filled thunderclouds. Author: Sofia Silvia Updated: 7:38 PM PDT July 21, 2021 When thinking about wildfires, we often think about its impact on our land, community and neighbors. But there is something else to consider: the atmosphere. PyroCbs, short for pyrocumulonimbus clouds, are often referred to as thunderclouds, a type of plume that mixes smoke particles in the upper atmosphere linking to storm elements like lightning or hail. It’s a phenomenon that you might see in a volcanic eruption – and now wildfires.