In September 2023, a spatially compounding event affected Europe, with an intense heatwave over northern France and nearly simultaneous extreme floods over the Iberian Peninsula and Greece. These extremes were accompanied by a low-high-low pressure system known as Omega pattern. However, the capability of climate models to reproduce such complex extremes and related atmospheric circulations is still unclear. By introducing a novel index, here we show that the 2023 event was not unique yet most extreme in recent decades. Using ensemble boosting, the fully-coupled Community Earth System Model 2 can reproduce such co-occurring extremes with remarkably similar configurations of the large-scale flow and even higher heatwave/rainfall than observed. This suggests that similar compounding events with even stronger intensity could, in principle, occur. However, such spatially compounding events are too rare in the model relative to reanalysis, suggesting that the model may underestimate their future occurrence in a warming climate.