From memory, the clouds up there this morning were cumulonimbus.

The thing that the symbol indicates is a cumulonimbus cloud.

This can occur with any cumulonimbus cloud when instability is high.

Were there only a few, their particles spread thinly through the mass of cumulonimbus?

"Continuous cloud cover below, cumulonimbus by the look of them.

Cumulonimbus, the biggest clouds of all, can also produce thunderstorms.

Cumulonimbus may form alone, in clusters, or along cold front squall lines.

Cumulonimbus clouds were building above them like huge cathedrals.

He ends up being turned to ashes by a lightning bolt inside a Cumulonimbus cloud.

This water vapour then rose upwards and created large cumulonimbus clouds.

Viewing scud clouds means that there is a cumulonimbus parent cloud.

In 1993, scientists discovered lightning bolts that shot upward from the top of a cumulonimbus cloud.

The vehicle stood where we had left it, grey cumulonimbus issuing from its gaping windows.

Near the end of the competition the weather deteriorated with cumulonimbus clouds and rain showers.

Like other precipitation in cumulonimbus clouds hail begins as water droplets.

The Tribe contracted into a small yellow cumulonimbus.

Here and there a cumulonimbus was growing in the thermals, threatening to develop into an afternoon thunderstorm.

Blowing up from astern are gigantic clumps of cumulonimbus clouds.

Even the smallest cumulonimbus clouds dwarfs its neighbours in comparison.

Cumulonimbus clouds are the final form of growing cumulus clouds.

Cumulonimbus, the largest of all cloud genera, has the capacity to produce very heavy showers.

"Scattered cumulonimbus cells with heavy precipitation and limited visibility at surface.

A miniature cumulonimbus cloud puffed from the oven.

Cumulonimbus clouds boiled furiously over the mountain's shoulder.

The cumulus were full cumulonimbus now, blocking sunlight.