Using the Feb 2018 "Beast from the East" SSW to illustrate the point that the zonal winds at 60°N do not generally reverse to easterlies much below 20-30 hPa.

In the zonal-mean, it's the *anomalous* weakening which propagates downward (i.e., the negative Northern Annular Mode). pic.twitter.com/fltEOlWgJ6

— Dr Simon Lee (@SimonLeeWx) January 5, 2021