Polar Vortex Collapse, Arctic Freeze Imminent
By Andrew at 9:24 AM The model forecasts above both show big high pressure centers interrupting the polar vortex and splitting it into two pieces. Such a split exemplifies the traditional weakening of the polar vortex. When that polar vortex is weakened, the cold air locked up in said polar vortex flows south, possibly into North America, maybe into the US. This is a very good sign coming from the models at this point in time to go along with the stratospheric observations.

Continuing with watching the models, we turn to a charted forecast of the ECMWF model. I want you to look at the bottom image, called the EP Flux. In short, the EP flux shows the direction and strength (shown by length of arrow) that air moves into the stratosphere. In events where warm air enters the stratosphere, long, extended arrows are commonly seen. The forecast into the days before New Year's Day show a batch of extended arrow motions, suggesting a large motion of warming may be incoming into the stratosphere. This enhanced EP Flux would theoretically enhance warming potentials in the Arctic, thus further weakening the Polar Vortex. I find it likely that the aforementioned 50mb wave over East Asia would be to blame for this rise in EP Flux values.... [link to theweathercentre.blogspot.de]