Climate change's influence on Cut-off Lows in the future

Cut-off Lows (COLs) are mid-latitude storms that are detached from the main westerly flow. They tend to propagate slower than other mid-latitude storms and are often harbingers of heavy and persistent rainfall. COLs have long been subject to thorough studies that have examined the physical structure and climatology across both hemispheres, however, their assessment in models is relatively low. In fact, there is no study on future changes in COLs in models. In this study, we analyze the cut-off lows in the northern hemisphere in the historic and future time slices in the CMIP6 dataset to study the frequency, duration, and intensity of the cut-off lows alongside the changes in velocity. Results show that the COL season, which is currently mostly limited to summer, extends into spring over Europe, North America, and Asia. This rise in activity in spring is more pronounced for COLs that are long-lasting and also have higher intensity maxima, i.e., the most impactful ones. Moreover, COL propagation velocity for persistent systems is due to slow down over North America in the summer. Slow-moving COLs are known to cause heavy localized rainfall. Through this study, we fill the information gap on the first insights of projected future changes in COLs by using TRACK to detect and trace COLs in the SSP5-8.5 projections of the CMIP6 ensemble.