Ask the Weather Guys: What are pyrocumulus clouds?

Q: What are pyrocumulus clouds?

A: A pyrocumulus is a fire cloud.

A pyrocumulus cloud forms from rising air that results from intense heating of the surface by phenomena such as wildfires or volcanic eruptions.

The fires that generate these clouds can be man-made or natural. A big fire produces strong upward-moving air currents that carry water vapor and ash upwards. The water vapor can condense on the ash forming cloud drops. The vigorous upward motions produce these pyrocumulus clouds that look similar to thunderstorm clouds, which also form due to strong upward-moving air.

In Latin, “pyro” means “fire” and “cumulus” means “pile up.” Cumulus clouds are those puffy-white clouds with tops that have a cauliflower appearance.

Pyrocumulus clouds are grayish or brown in color because of the ashes and smoke of the fire. The tops of these clouds can reach as high as 30,000 feet. It is difficult to locate the bottom of a pyrocumulus cloud as it is often obscured by the ash generated by the fire or the volcanic eruption.

If lots of water vapor is available, the pyrocumulus can develop into a cumulonimbus, or thunderstorm. When a thundercloud forms, it is called pyrocumulonimbus or a cumulonimbus flammagenitus cloud.

Like thunderstorms, pyrocumulonimbus can produce lightning because of the strong updrafts. Rain can also fall from these clouds, which could help extinguish the fire generating the cloud. Of course, the lightning might cause another fire.

Photos: Deaths, damage mount in Australian fires

Warning: Some photos contain graphic content.