Convective Available Potential Energy (CAPE), also known as positive buoyant energy. Units are Joules per Kilogram. A value of around 1000 J/K will support weak convection while 2000 J/K provides moderately strong convective potential. Values in excess of 4000 J/K are associated with large and severe thunderstorms. This is a net positive area in the sounding - any negative area in the cap has been subtracted out.