Over the next 16 days (in the GFS) the #PolarVortex first elongates under wave-2. Then, wave-2 declines & wave-1 takes over, with the Aleutian ridge intensifying following warming from the Siberian sector. The vortex core deepens ~60 dam in this period despite the weakening [U]. pic.twitter.com/70nL5DXhnf

— Dr Simon Lee (@SimonLeeWx) November 15, 2019