What defines a tornado?

A tornado is defined as a powerful and destructive weather phenomenon characterized by a rotating column of air that extends from a thunderstorm to the ground. This formation is associated with strong winds and typically occurs in severe thunderstorms, often in the context of low-pressure weather systems.

The option highlighting that it is a cyclone of low pressure with strong winds correctly captures the essence of a tornado. These systems are marked by rapid rotation and can have wind speeds exceeding 300 miles per hour, making them one of the most violent weather events. Understanding that a tornado is fundamentally connected to low-pressure systems helps in recognizing its formation conditions and the destructive potential associated with it.

In contrast, the other options describe different weather phenomena that do not align with the characteristics of a tornado. Calm weather, high-pressure systems, and warm fronts with light showers lack the rotational wind characteristics and the violent nature typically seen with tornadoes.