The persistence of the Summer North Atlantic Jet Variability: Dynamical Feedbacks and Model‐Observation Discrepancies

The North Atlantic (NATL) jet stream plays a central role in shaping weather and climate over the North Atlantic and Europe. It continuously fluctuates in latitude and strength, guiding storm tracks across the basin. When these fluctuations become unusually persistent, they can anchor weather regimes for extended periods, increasing the likelihood of extreme events such as droughts and floods. Here, we investigate the persistence of summer NATL jet latitudinal variability and of the closely related Summer North Atlantic Oscillation using CMIP6 models and the ERA5 reanalysis. Using the relative vorticity tendency equation, we quantify the strength of the eddy–mean flow feedback and show that it explains a large fraction of the intermodel spread in jet persistence. In contrast, differences in feedback strength do not account for the persistence discrepancy between models and ERA5, which we suggest arises from differences in sea–air coupling strength. We further find that intermodel differences in jet persistence are closely linked to differences in the persistence of European precipitation. These results underscore the importance of accurately characterizing dynamical uncertainty, as it directly translates into uncertainty in regional climate impacts.