CAPE

Convective Available Potential Energy (CAPE) is a measure of atmospheric instability - and hence how vigorously parcels of air can rise to produce clouds and, perhaps, showers or thunderstorms. The higher the value of CAPE the more energetic and severe the storms may be. In the UK, CAPE of 2000 Joules per Kg or more is indicative of high instability and potentially severe storms, with air rising at well over 100mph to produce towering thunderclouds.