100 hPa 60°N zonal mean winds -- a diagnostic for the strength of the lower-stratospheric polar vortex -- are currently date-record-weak & unusually weak for any time in winter. But the story is oddly complex & a-typical... 🧵 pic.twitter.com/nSNvhTNjnn

— Dr Simon Lee (@SimonLeeWx) December 4, 2022