Reason for planetary/Rossby wave amplitude during the winter months/in the winter hemisphere : meteorology

Sorry to spam with questions, but I am wondering why planetary/Rossby waves increase in amplitude in the winter, as is mentioned here: https://www.climate-policy-watcher.org/global-climate-2/waves-planetary.html in the last paragraph where they say “In the winter, when the planetary waves are significantly amplified…”

I would imagine it has something to do with the fact that zonal winds are stronger in the winter (because of the steeper temperature gradient), but I am having trouble seeing the connection. I know that there are relationships between the Rossby wave propagation and the background flow, does a stronger background flow increase the amplitude of the rossby wave somehow?