Convective instability

Convective instability (also known as potential instability or thermal instability) occurs when dry mid-level air rises (usually caused by mountains or hills) over very warm, moist air in the lower troposphere. The differences saturation cause changes adiabatic lapse rates, and can result in the air layer becoming unstable and possibly overturning.

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Convective instability is also termed static instability, because the instability does not depend on the existing motion of the air; this contrasts with dynamic instability.

High convective instability can lead to severe thunderstorms and tornadoes. This is because the moist air which is trapped in the lower layer; eventually a rising bubble of humid air breaks through the dry layer triggering the development of a cumulonimbus cloud.

Further reading

• Barry, R.G. and Chorley, R.J. Atmosphere, weather and climate (7th ed) Routledge 1998 p. 80-81 ISBN 0-415-16020-0