The rare case of <scp> Hurricane <i>Catarina</i> </scp> (2004) over the <scp>South Atlantic Ocean</scp> : The origin of its precipitation through a <scp>Lagrangian</scp> approach

Tropical cyclones (TCs) are extremely rare over the South Atlantic Ocean (SATL) due to predominantly unfavourable conditions, that is, cool sea-surface temperature and strong vertical wind shear. Nevertheless, unusual conditions SATL associated with a blocking system promoted formation of Hurricane Catarina from an extratropical precursor in late March 2004, which produced heavy rainfall states Santa Rio Grande do Sul south Brazil. This work identifies moisture sources for precipitation by along its 6-hourly trajectory, through Lagrangian moisture-tracking method. We extracted pathways precipitating air parcels within cyclone's outer radius global outputs FLEXPART model forced ERA-Interim reanalysis. Our findings revealed terrestrial source south-southeastern Brazil (SEB) oceanic limited box between 20-40°S 30–50°W (WSATL) as principal sources, overall support ∼27% ∼66%, respectively. However, their contribution varied according development phase Catarina. While uptake SEB decreased ∼75% during ∼8% hybrid stage, WSATL notable increased ∼20% 87%, Likewise, contributions tropical cyclone accounted ∼13% ∼85%, The tracked achieved high water content short period before precipitation, leading reduction mean vapour residence time ∼3.1 days. Additionally, trajectory was noticeably higher than climatological value.