GFS 00Z strongly amplifies wave-2 through to ~50 hPa on Dec 17th, with two "legs" of the vortex in the eddy height field as the 10 hPa vortex drifts toward Baffin Bay. The pattern subsequently decays in this run, but persistent Scandi-Ural blocking remains in the forecast... http://twitter.com/SimonLeeWx/status/1334434703424835584