Cold Pool

A cold pool is a pocket of dense, cold air that forms when rain evaporates during intense precipitation, such as underneath a thunderstorm or a precipitating shallow cloud, and it typically spreads outward at around 10 metres per second and lasts two to three hours over both land and ocean. It forms because evaporating rain falling through unsaturated air draws in latent heat, cooling and densifying that air, while falling raindrops also drag the surrounding air down with them, together producing a sharp drop in surface temperature and an outward-spreading gust front. As the cold pool spreads, downdrafts push dry, cold air into the boundary layer and dry out its center, so that when the gust front passes over a location, wind speed jumps while humidity and temperature both drop suddenly.