The large-scale midlatitude flow is dominated by Rossby wave activity

along the upper-level midlatitude wave guide and jet stream. In the

Atlantic-European region this activity occurs in preferred

quasi-stationary, persistent states, so-called weather regimes. In this

presentation physical and dynamical processes impacting the prevailing

Rossby wave pattern and weather regimes are elucidated with focus on

"diabatic outflow" driven by cloud-condensational processes in

synoptic-scale weather systems. Furthermore, the impact of these

multi-scale interactions on extreme weather events and predictability

are explored.