A plume of potentially warm air (see potential temperature) that originates over Mexico and flows towards the United States at an intermediate level, where it forms a capping inversion. Extremely high humidity builds up in the lower layers, partly through advection of moist air from the Gulf of Mexico. When an upper-air trough approaches from the west, the capping inversion may break down completely, giving rise to exceptionally powerful multicell and supercell thunderstorms over Texas, Arkansas, and Oklahoma. See also Spanish plume.
Subjects: Meteorology and Climatology.