Joh Foster (Member 65,232) spotted a family gathering of convection clouds over Chandler’s Ford, Hampshire, England. Convection clouds develop from thermals rising off sun-warmed ground or warm water. If they grow tall enough, they can produce showers.

Among Joh’s cloud family were Cumulus on the horizon, rising through the crisp, clear air. The ones that had grown taller from base to summit than the height of their bases above the ground are known as Cumulus congestus. Joh’s were close to maturing into fully fledged Cumulonimbus storm clouds – like the one looming in the foreground.

This was a Cumulonimbus capillatus, ‘hairy’ in Latin, with an upper anvil, or incus, composed mostly of ice crystals. Rounded cloud pouches known as mamma hung beneath its incus. These form where air in the anvil cools and sinks in smooth, moisture-laden pockets, dragging the cloud down with them: convection currents again, but this time descending rather than rising.