Which factor is NOT required for thunderstorm formation?

Thunderstorm formation typically requires three main factors: lifting action, moisture, and an unstable lapse rate. Lifting action, such as that provided by weather fronts, terrain, or convergence of air masses, is essential as it helps to elevate warm, moist air into the atmosphere. Moisture is crucial because it provides the necessary water vapor that condenses to form clouds and precipitation. An unstable lapse rate, which refers to a situation where the temperature decreases rapidly with altitude, also plays a key role in allowing air to rise effectively, leading to the development of thunderstorms.

High pressure, on the other hand, is not a factor that contributes to the formation of thunderstorms. In fact, high-pressure systems are generally associated with stable weather conditions, which are not conducive to the development of the instability required for thunderstorms. Therefore, recognizing that high pressure does not contribute to the dynamic processes needed for thunderstorm formation allows us to accurately identify it as the correct choice in this context.