Sea-breeze thunderstorms are considered a type of air-mass thunderstorms because they typically develop within a single, relatively homogeneous air mass, and their formation is largely driven by local heating and cooling processes rather than the convergence of different air masses.
Here's a more detailed explanation:
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Air Mass Characteristics: Air-mass thunderstorms form in areas where there is minimal horizontal movement of different air masses. In the case of sea-breeze thunderstorms, they typically occur in coastal regions where the land heats up more quickly than the sea during the day. This temperature difference creates a thermal gradient.
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Local Heating: During the day, the land absorbs heat from the sun, causing the air above it to warm and rise. In contrast, the ocean remains cooler, leading to relatively stable air over the water. As the warm air rises over the land, cooler and denser air from the ocean (sea breeze) moves in to replace it.
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Convergence: The interaction between the cool sea breeze and the warm air rising over the land leads to localized convergence, which can cause thunderstorms to develop. The uplift of the warm air can generate cumulus clouds, which can grow into cumulonimbus clouds (thunderstorm clouds) as the process continues.
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Short-lived Nature: Sea-breeze thunderstorms are typically short-lived and localized, often forming in the afternoon when the land heating is at its peak. This characteristic is also common among air-mass thunderstorms, which usually develop in warm, moist, and unstable air conditions but tend to dissipate relatively quickly once the heating diminishes.
In summary, sea-breeze thunderstorms are categorized as air-mass thunderstorms due to their reliance on localized thermal dynamics and the resulting weather phenomena that occur within a single air mass, rather than the interactions of multiple air masses, which might characterize other types of thunderstorms (like frontal thunderstorms).