Convective available potential energy

This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts, without removing the technical details. (November 2014) (Learn how and when to remove this message)

In meteorology, convective available potential energy (commonly abbreviated as CAPE),^[1] is a measure of the capacity of the atmosphere to support upward air movement that can lead to cloud formation and storms. Some atmospheric conditions, such as very warm, moist, air in an atmosphere that cools rapidly with height, can promote strong and sustained upward air movement, possibly stimulating the formation of cumulus clouds or cumulonimbus (thunderstorm clouds). In that situation the potential energy of the atmosphere to cause upward air movement is very high, so CAPE (a measure of potential energy) would be high and positive. By contrast, other conditions, such as a less warm air parcel or a parcel in an atmosphere with a temperature inversion (in which the temperature increases above a certain height) have much less capacity to support vigorous upward air movement, thus the potential energy level (CAPE) would be much lower, as would the probability of thunderstorms.

More technically, CAPE is the integrated amount of work that the upward (positive) buoyancy force would perform on a given mass of air (called an air parcel) if it rose vertically through the entire atmosphere. Positive CAPE will cause the air parcel to rise, while negative CAPE will cause the air parcel to sink. Nonzero CAPE is an indicator of atmospheric instability in any given atmospheric sounding, a necessary condition for the development of cumulus and cumulonimbus clouds with attendant severe weather hazards.