CAPE (Convective Available Potential Energy, in J/kg) quantifies the cumulative buoyancy of an air parcel rising from the surface to its equilibrium level. Values above 1,000 J/kg indicate moderate convection; above 2,500 J/kg, high potential for severe storms with large hail and tornadoes.
Use in forecasting
It is calculated from soundings and numerical models. High CAPE combined with strong wind shear is the classic recipe for supercells. In Spain, Mediterranean CAPE values can exceed 3,000 J/kg in autumn, fuelling storms that produce torrential rain.