so what you are saying is, there is a sub tropical "warm front" that keeps pushing northward (CC induced). Only, it is hitting the polar jets further north than it typically would have pre-CC era. However, recently over the past 10-20 years, it has made it so far north during the winter season that a stronger battle has developed ie...stronger geostrophic winds? Just trying to see if I am on the right path of understanding what you have posted...