Hey Ray: The CAP
PITTSBURGH (KDKA) -- There is a term you probably heard a meteorologist use before when talking about thunderstorm chances. That term is "The Cap."
Think of the air at Earth's surface like a hot air balloon. The air in the balloon needs to be hotter than the air around it, or you would just be sitting on the ground in a floppy balloon, connected to a basket. That is because warm air is more buoyant than colder air, so it lifts.
Lifting warm air from the Earth's surface is referred to as a "parcel of air" and is a major ingredient for thunderstorms. That rising air carries moisture high up into the atmosphere as long as the air around it is colder. Just like a hot air balloon.
If the rising air encounters a layer of warm air, that lifting stops, cutting off a storm's ability to form. That layer of warm air is what we call "the cap,"
It is capping off the atmosphere, sort of a like a lid. That prevents the warm parcel of air from lifting to storm developing heights.
If there is no "cap", a thunderstorm will form. If the cap is weak, some of that air can break through the cap!
This happens if the heating at ground level is sufficient enough. Sometimes "caps" are weak. This allows the parcel of warm air to break through. When this happens, strong storms usually occur.
These storms are typically strong because once that parcel of air gets beyond the cap, the atmosphere surrounding it is usually quite colder. This means that the parcel of air can lift quite far quite quickly, enhancing storm development.
