Środowiskowe Seminarium Fizyki Atmosfery

Tropical cyclones are among the most destructive natural phenomena, threatening lives and property. However, the physical mechanisms that drive their genesis still need more investigation. In this talk, the genesis of a Tropical Cyclone (TC) Seroja will be discussed. Seroja formed over the Maritime Continent and in April 2021 brought historic flooding and landslides to southern Indonesia and East Timor, and also impacted Western Australia. Its genesis in the Indonesian region of Timor and Suvu Seas was associated with enhanced equatorial convection on March 28, 2021 which was preceded by warm sea surface anomalies in that region. This equatorial convection developed on the leading edge of Madden-Julian Oscillation (MJO), ahead of the convective phase. The initial equatorial convection moved southwest, boosted by environmental cyclonic vorticity associated with convectively coupled equatorial Rossby wave. The interaction between Rossby wave and two convectively coupled Kelvin waves embedded within the larger-scale envelope of the MJO provided supportive environment for strengthening of TC Seroja precursor. Each of the two Kelvin Waves that arrived over the Maritime Continent had a unique contribution in this event; structuring the convection, winds and precipitation patterns. This concurrence of factors created perfect storm conditions and led to the genesis and development of TC Seroja - one of the first tropical cyclones to have a significant impact on Indonesian land. These results indicate that forecasting of TCs genesis and tracks should consider the dynamics of tropical waves in the Maritime Continent.