Pyrocumulus and pyrocumulonimbus clouds are usually created by fires but sometimes they can be created by lava flow. We witnessed these clouds and associated thunderstorms in 2018 with the Kileauea eruption and we saw them again yesterday with the Mauna Loa eruption.
In order for thunderstorms to develop, a few things are needed. The two most important things are moisture in the air and lift of air in the atmosphere. The higher the lift, the more that water condenses from the water vapor in the air. The hotter the ground, the more lift can be created. Obviously, lava is very hot so it produces great lift to create not only pyrocumulus clouds, but it can also provide enough lift to create pyrocumulonimbis clouds.
Pyrocumulonimbus clouds are pyrocumulus clouds that produce thunderstorms.
We talked to Robert Bohlin, a meteorologist from the Honolulu Forecast Office Information for the National Weather Service to get more details on these types of clouds.