You probably already realised, but the GEFS has a weak bias so far this winter when it comes to the stratospheric #PolarVortex.
— Dr Simon Lee (@SimonLeeWx) January 28, 2020
On average, a day-16 GEFS ensemble-mean forecast has been ~15 m/s too weak. In contrast, the new GFS has a slight strong bias. pic.twitter.com/vbp51eYfnA