Relation Between Cyclone Evolution and Fetch Associated With Extreme Wave Events in the South Atlantic Ocean

Abstract

The goal of this work is to investigate the fetch patterns and configurations associated with extratropical cyclones that promote extreme wave events in the western portion of the South Atlantic Ocean. Cyclones are identified and tracked using an objective algorithm and linked to winter extreme Hs events in 10 years of ERA5. The results show the occurrence of 10.7 ± 3.2 winter storms associated with extreme waves within the domain. The cyclone size and intensity show that extreme waves occurring within the domain are mainly related to the intensification stage of the cyclones in the region. There is no relevant difference between mean wind and wave direction during the event, being the SW/W directions dominant. The analysis of the fetch evolution during the lifecycle of the cyclones associated with the most extreme events showed that the surface winds present their maximum usually 10 h–24 h before the maximum Hs. Although large fetches develop along the continental shelf, usually within the cold sector of the cyclone, the Hsmax are located northwestward from the cyclone's center, in the downwind end of the fetch. At the end of the event, the extreme region detaches from the cyclone fetch while still propagating northeastward. At this stage, the swell waves are dominant, with a large peak period and wave age.