...To understand Rossby waves, one has to understand the subtle noninertial effects that the rotation of the Earth about its axis has on the atmosphere. Most important are the apparent Coriolis “forces” that influence the horizontal movement of an air parcel, for example, in the jet stream. These Coriolis effects are strongest at the poles and weakest at the equator. As a result of this gradient with latitude, the Coriolis effect can act as a restoring force on air parcels that are displaced north or south of their “normal” latitude, and hence lead to an oscillation. The key effects, which can systematically displace such air parcels north or south, are associated with the flow of air over big mountain ranges like the Rockies or Himalaya, or differential heating by continental/ocean temperature contrasts (because these systematic forcing effects are so much stronger in the Northern Hemisphere, so too are quasistationary Rossby wave amplitudes).
Our climate system is not just a static thermodynamic system, it is a fluid dynamical system, and the effects of dynamics (especially on a rotating planet) can often be counterintuitive...
). So this year the cold in the Eastern US has been matched by warmth in the Bering Sea and Alaska.
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