Polar vortex The polar vortex is a persistent large-scale cyclonic circulation pattern in the middle and upper troposphere and the stratosphere, centered generally in the polar regions of each hemisphere The polar vortex is not a surface pattern. It tends to be well expressed at upper levels of the atmosphere(> 5 km)Polar vortex • The polar vortex is a persistent large-scale cyclonic circulation pattern in the middle and upper troposphere and the stratosphere, centered generally in the polar regions of each hemisphere. • The polar vortex is not a surface pattern. It tends to be well expressed at upper levels of the atmosphere (> 5 km)