Climate systems behind the observed singularities of the very intense tropical cyclone FREDDY

Abstract The very Intense Tropical Cyclone (ITC) FREDDY has broken many records in the climatology of Tropical Cyclones in Mozambique in recent years. It has been unique regarding the lifetime, the travelled distance, the trajectory and the number of landfalls. This research aims to examine the atmospheric conditions or systems behind all observed singularities. Data from the fifth generation of atmospheric reanalysis (ERA5) provided by the Copernicus Climate Change Service (C3S) were used to achieve this purpose. We have used hourly data of different climate variables, such as, sea surface temperatures (SSTs), mean sea level pressure (SLP), wind, and relative humidity, to identify and characterize different climate systems, synchronized with the manifestation of FREDDY. In general, results indicate that FREDDY’s lifetime was influenced by the combination of two factors, the warm waters from the Southwestern Indian Ocean (SWIO), whose SSTs varied from 27 oC to 32 oC, and the southern subtropical High Pressure Systems (HPS), enhancing moisture to the cyclone in the continent through its confluent winds at low levels. On the other hand, the Subtropical Jet Streams (SJS) had contributed to its singular trajectory, leading to multiple landfalls. The upper Trough and upper Ridge associated with the SJS, positioned respectively over the Austral Africa and southern Madagascar, had determined the back-and-forth movement of FREDDY through the Mozambique Channel, hitting both countries, Mozambique and Madagascar. These findings provide important clues that may help the cyclone monitoring at national and regional levels, and anticipate necessary actions to minimize its negative impacts.