Convective precipitation is generated by rising currents of warm, moist air (convection) that ascend rapidly, cool, and condense to form clouds of great vertical development, especially cumulonimbus. It is characterised by being intense, localised, and short-lived, unlike stratiform precipitation (associated with fronts, more widespread and moderate).
Triggering mechanisms
Convection can be initiated by: solar heating of the ground (summer afternoon thunderstorms); surface convergence (sea breezes, gust fronts); orography (terrain forcing air upward); or dynamic instability (DANAs, troughs). The available energy is measured by CAPE (Convective Available Potential Energy): values above 1,000 J/kg indicate risk of severe storms.
In Spain, convective precipitation is especially significant in the Mediterranean, where the warm sea provides enormous quantities of moisture and energy. Autumnal DANAs can generate accumulations of 200-500 l/m² in a few hours, causing flash floods. The localised nature makes prediction extremely difficult: one town may receive 300 l/m² while 20 km away it barely rains.
Weather radars and satellites are the key tools for detecting and tracking convective precipitation in real time. See also: lake-effect snow, graupel.