Ritter,
The Jetstream has Rossby waves on it, whereas water waves travel across the water, and cause the surface to go up and down, Rossby waves travel around the Jetstream and cause the Jetstream to meander north to south. These meanders are what is being affected by Arctic Amplification (what Francis seems to be saying), Arctic Amplification is the term used to describe how the Arctic warms faster than the rest of the globe.
What happens during Warm Arctic Cold Continents (WACC) pattern events is that the polar vortex breaks down or reverses (as it did in 2009/10's winter). Normally the polar vortex keeps cold Arctic air in the Arctic, when it breaks down it allows that air out, but also allows warmer air in from lower latitudes, so some lower latitude areas get cold outbreaks (e.g. Northern Europe), other regions further north experience unusually warm weather. If you left the freezer door open the kitchen would get colder than usual, but the Freezer would be warmer than usual.