GFS & GEFS 00Z 0.5° ensemble plume
The ERA5 climatology uses 00Z values from 1 January 1979 through 30 June 2020 inclusive. Members exceeding 41.2 m/s are classified as having a “strong vortex event” following Tripathi et al. 2015, whilst those with winds below 0 m/s indicate either a major sudden stratospheric warming (SSW) or the final stratospheric warming (FSW). GEFS members with a strong vortex are only shown in blue if there are no members with easterlies, to avoid any potential overlap.
GFS 0.5° forecast evolution
GEFS 0.5° ensemble-mean forecast evolution