The other big player here is QBO structure...I wish Sam Lillo still posted here but he did some amazing work with (I am pretty certain he developed this) the MQI. The research showed strong correlation to structure/SSW potential and influences on the stratosphere and upper troposphere.
Speaking of ozone...I've wanted to look into this but is it possible all that smoke from the wildfires this summer/fall could play a big factor into the stratosphere and how it evolves...like doesn't smoke impact ozone production?