Why can't a jet stream cause a tornado?

Answer 1

The jet stream produces wind shear, or differences in wind speed and direction with changing height. Wind shear is a necessary ingredient for producing tornadoes, but on its own it can't do much.

To get tornadoes you need thunderstorms. When thunderstorms develop in strong enough wind shear they can start to rotate. This rotation can the develop into a tornado. But this sort of rotation cannot be produced by wind shear alone.

Answer 2

Jet streams are fast-moving, high-altitude air currents that do not typically reach the surface of the Earth where tornadoes form. Tornadoes form due to the interaction of different air masses at the surface, not from high-altitude winds. While jet streams can influence weather patterns and contribute to the conditions that are favorable for tornado formation, they do not directly cause tornadoes.