This is a nice example of the perturbation of initial conditions in ensemble forecasting: only 8 of the 21 GEFS members were initialized at 00Z with an easterly 10 hPa 60°N zonal wind (i.e. still in major #SSW state).
The vortex is now in recovery mode! pic.twitter.com/ZQAaSkVcTN

— Dr Simon Lee (@SimonLeeWx) January 23, 2019