Generally wind speeds greater than 57 mph and can be upto 200 mph.

• Tropopause Jets - Occur just below the tropopause ~ 10-15 km altitude or 200-300 mb pressure levels.
• 4 Tropopause jets in the Northern Hemisphere
• Polar Vortex: North of 75 N; westerly wind; winter time Polar fronal Jet: ~60 N; westerly wind; winter time Subtropical Jet: ~30 N; westerly wind; winter time Tropical Jet: ~15 N; easterly wind; summer time
• Caused by temperature gradients, which in turn produce pressure gradients