The lapse rate of the Mexican air will eventually overcome that of the cloudy Gulf air below, causing extreme convective instability. As the clouds rise, they become progressively warmer than the ambient air and will continue rising until tapering off at the stable tropopause. Now, more warm humid air below has an efficient path for rapid ascent high into the troposphere thorough strong convective updrafts. It is here that the second of the two features has significant effect. The jet stream, similarly oriented to the cold front, provides for significant vertical wind shear, distributed through a sizable depth of the troposphere.
Wind shear is vital in the formation of powerful, long-lasting and consequently severe storms.
In supercell thunderstorms this prevailing layer of wind shear provides for a single, organized convective cell. The air at the surface, slowed by friction, is considerably slower than the winds aloft. This condition forms a measure of vorticity rotating about a horizontal axis, as would a paddle wheel if placed with the upper paddles in the air aloft, and the bottom paddles in the slower winds at the surface. The convecting air will now rise into the couplet. One might expect the system to travel in the direction of the air in the middle troposphere, as do ordinary air-mass thunderstorms.