Some recent ECMWF deterministic runs have been predicting a very intense tropospheric "polar vortex" over the high Arctic next week, with minimum 500mb heights below 4600 gpm. The ERA5 record since 1979 is 4544 gpm (in Jan 1993, which also holds the monthly +AO record). pic.twitter.com/nj5Y6DxLWn

— World Climate Service (@WorldClimateSvc) December 24, 2019