True or False: An airmass thunderstorm is produced by localized convection in an unstable airmass.

An airmass thunderstorm is indeed produced by localized convection in an unstable airmass, making the statement true. These thunderstorms typically develop in warm, humid conditions where the air near the surface is heated, causing it to rise. As the warm air ascends, it cools and condenses, forming clouds and precipitation, which are characteristic of thunderstorms.

The key factor is the instability of the airmass. When an airmass is unstable, it means that the warm air can continue to rise without significant resistance, leading to the development of strong updrafts. This process is more common in summer when the surface temperatures are higher and conditions are more favorable for such convection. Therefore, while it can depend on the specific weather conditions and location, the fundamental mechanism behind airmass thunderstorms is always based on localized convection in an unstable airmass.