A new tool was developed to track changes in the Arctic stratospheric polar vortex over many years. It shows that after sudden warmings, there are long-lasting warm anomalies in the lower stratosphere called polar-night jet oscillation (PJO) events. These events are seen in different datasets and models, and they affect the polar vortex recovery time. PJO events happen after about half of major sudden warmings and are linked to weak vortex events in the atmosphere. They play a role in seasonal forecasting due to their long-lasting effects and influence on the troposphere.