Great write ups in here.
Something that I have seen regarding prominant early season split vortices (that may not quite produce a full SSW), is the Greenland plateau wave break. For us in the UK this has produced the most severe of arctic flows and has lead to a trop based Greenland high. I used to call this an 'internal' wave break as opposed to the 'external' wave break that a strong Himalayan MT can produce. The external wave break sees the strat vortex fall like a pack of cards as the tilting 'wobble' brings down the pack of cards from the top down. However, the 'internal' wave