What is the expected icing condition when associated with Cumulonimbus clouds?

Cumulonimbus clouds are associated with significant vertical development and are often linked to severe weather phenomena. These clouds typically form in unstable atmospheric conditions and can reach high altitudes, where temperatures are significantly lower. The intense updrafts and downdrafts within these clouds can lead to supercooled water droplets, which are liquid water droplets that remain in liquid form even at temperatures below freezing.

When an aircraft encounters Cumulonimbus clouds, the likelihood of experiencing icing is considerably increased due to the presence of these supercooled droplets. The extreme weather conditions typically associated with Cumulonimbus—such as thunderstorms, turbulence, and potential hail—contribute to a higher risk of serious icing compared to other cloud types.

In this context, the correct response indicating expected icing conditions is serious icing, as pilots should be particularly cautious when flying in or near these clouds due to the potential for severe icing hazards impacting aircraft performance and safety.