Which type of cloud is indicative of thunderstorm conditions, characterized by large, dense towers that may reach altitudes of 75,000 feet?

Cumulonimbus clouds are indeed indicative of thunderstorm conditions and are characterized by their large, towering structure. These clouds can extend vertically and reach altitudes of up to 75,000 feet, making them some of the tallest clouds in the atmosphere. The development of a cumulonimbus cloud typically involves strong vertical air movements, which can result in severe weather phenomena such as heavy rain, lightning, hail, and even tornadoes.

This cloud type is a key component of the thunderstorm development process, as it forms when warm, moist air rises and cools at high altitudes, allowing for the condensation of water vapor. The robust formation of cumulonimbus clouds often signifies unstable atmospheric conditions, which are necessary for the development of thunderstorms.

In contrast, cirrus clouds are high-altitude clouds that are thin and wispy, altostratus clouds are mid-level clouds that cover the sky and can indicate precipitation but do not typically lead to severe weather, and nimbus clouds refer to rain-producing clouds in general but do not specifically describe the towering structure associated with thunderstorms.