English: This animated skew-T plot (see color code) alternates between the results of a morning sounding with surface temperature around 23°C, and those of an afternoon sounding with surface temperature around 30°C. The thick red line is temperature, and the thick green line is the dew point. Around 2km to 3km altitude, the morning sounding shows a depression in the dew point curve (dew point depression, also called a hydrolapse). Below this, from 1300m to 1800m, the morning sounding shows a layer with unusually constant temperature (red line follows the 10°C isotherm). As moisture below the dew point depression begins to saturate the mid level air, it lowers the temperature there. The red curve moving to the left shows the cooling. The net result is that the air at this altitude becomes negatively buoyant in comparison to the surrounding air. This makes the layering convectively unstable and may lead to severe convection in the form of thunderstorms.