NH #polarvortex is predicted to strengthen to nearly 65 m/s at 10hPa over the next week. This strengthening is occurring from the bottom up, with large changes also in the lower stratosphere at 100hPa and accompanying +3 sigma values of the Arctic Oscillation. pic.twitter.com/V4Fi1o6GnJ

— Dr. Amy H Butler (@DrAHButler) January 7, 2020