Pyrocumulus

Pyrocumulus refers to a type of cloud that forms when intense surface heat from a wildfire or volcanic eruption drives strong convective updrafts. The rising hot air carries smoke, ash, and water vapor into the atmosphere. As the plume cools and expands, the moisture condenses into a cumulus-like cloud that can resemble a puffball or mushroom-shaped column and may reach several kilometers in height. The cloud is composed mainly of condensed water droplets, but may contain ash and aerosol particles from the source eruption or fire.

Pyrocumulus is distinguished from pyrocumulonimbus, which is a thunderstorm produced by pyroconvective processes. If convection intensifies enough to form strong updrafts and charge separation in the cloud, lightning and more energetic weather phenomena such as gusts, rain of ash, or even hail and tornadoes can occur; in that case the plume is called a pyrocumulonimbus. Pyrocumulus clouds can nonetheless influence local weather by enhancing vertical mixing and creating gusty winds at the surface, as well as by distributing embers or ash.

Observations of pyrocumulus are common near large wildfires and active volcanic vents. Their appearance and development can provide a qualitative indicator of fire intensity and plume dynamics, though they are part of a broader spectrum of pyroconvection and should be interpreted with caution.