ATPL Canadian Meteorology, Radio Aids to Navigation, and Flight Planning (SAMRA) Practice Test

Unstable warm air masses are characterized by the development of convective clouds. This occurs because warm air is less dense than the surrounding cooler air, allowing it to rise more readily. As the warm air ascends, it expands and cools, leading to condensation, which contributes to cloud formation. This process often results in the development of cumulus clouds, which are typically associated with unstable conditions and can lead to turbulence, thunderstorms, and other convective weather phenomena.

In contrast, layered clouds are generally associated with stable air masses, where the atmosphere does not allow for significant vertical movement. Minimal vertical growth of clouds also pertains to stable conditions, as does the dominance of stratiform cloud types, which are usually formed in more stable atmospheric conditions. Therefore, the characteristics of unstable warm air masses align closely with the development of convective clouds, making it the correct choice.