What is jet stream and vorticity?

JET STREAM - a very strong airflow occurring near the tropopause. It is most often seen on weather maps at 300 hPa (about 9 km). It is characterised by a large wind speed gradient (decreasing wind speed per unit distance from the p.s. axis). The wind speed gradient is a measure of the vorticity that is transported to the lower layers of the atmosphere becoming a starter low on the atmospheric front. If there is no generation of a low, then the isobars take on a cyclonic curvature or change their previous curvature towards a cyclonic curvature. The changes described above take place in the area to the left of the p.s. axis, in the area to the right of the p.s. axis the anticyclonic vorticity is transported.

VORTICITY - is defined as the rotation of a speed vector. The term made a career when in the 1940s a theory of the development of baric systems was formulated; the change in vorticity was taken as a measure of the development of a low or a high, rather than a mere drop or rise in pressure.