Illustration of two situations for the polar jet stream: Text: The polar vortex is a large area of low pressure and cold air over Earth's North and South Poles. When the jet stream weakens, it becomes wavier, allowing that cold air to dip southward in places while warmer air pushes northward elsewhere. A large pressure difference helps keep a strong jet stream on a straighter path, which keeps the cold air over the Arctic When the jet stream weakens, it becomes wobblier, allowing cold Arctic air to move southward
https://cdn.mastdn.ca/media_attachments/files/111/754/483/953/775/958/original/690e5463f66d14f9.jpeg