Yeah, you know - that is intriguing! It kind of reminds me of simply balancing forces in vector calculus from them college days... A lot of fancy schmancy terms for what is simply adding up all the vectors and balancing them out.. This can be done with trigonometry, by use of variations in soc-cah-toa (sine over cosine...etc)...

Hypothetically only, I think what may be going on is a strengthening vectorial component (perhaps more so than the models intimate) oriented from S toward the N...Meanwhile, there is a weakening vectorial component oriented from NE toward the SW... In very simply terms, the one from the S is becoming increasingly dominant in the addition. But, without hand on availability to the latest sounding data and the inside scoop on recon that I suspect we don't "really" get to see some times - wink wink - this has to be suppositional...