EGU General Assembly 2020
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On the role of tropical waves triggering extreme rainfall and flood in Sulawesi, Indonesia: a multi-scale interaction perspective

Beata Latos, Thierry Lefort, Maria Flatau, Donaldi Permana, Piotr Flatau, Dariusz Baranowski, Jaka Paski, Erwin Makmur, and Eko Sulystyo
Beata Latos et al.
  • Institute of Geophysics, Polish Academy of Sciences, Atmospheric Physics, Poland (

On January 22, 2019 extreme rainfall in the South-Western Sulawesi, Indonesia, triggered a massive, deadly flood, the most devastating one ever reported. This happened during an interaction of a robust Convectively Coupled Kelvin Wave (CCKW) and Equatorial Rossby Wave (ER). Potential causes of a flood include Madden Julian-Oscillation active phase, rainy season with monsoonal flow in the Karimata Strait, positive sea surface temperature anomalies supportive of convection, and synoptic-scale weather systems. All these factors can contribute to extreme rainfall and a flood development. Nonetheless, here we show that in this particular case enhancement of low-level westerlies led to convergence and forced ascend of moist air over orographic features of the south-western Sulawesi. This chain of processes was a result of a propagation of a CCKW, with contribution from an ER. Satellite and radar data analysis, as well as in-situ observations reveal that convergence and strong westerlies in the Java Sea, forced by the CCKW, resulted in the rain events in Jeneberang River Basin and the devastating flood in the city of Makassar.

Additional analysis of 20 years of the flood database together with in situ observations and satellite data support our hypothesis, based on this case study, of a significance of an enhanced westerlies as a precursor of extreme rain events and floods in Makassar, the capital and most populous city in Sulawesi.

How to cite: Latos, B., Lefort, T., Flatau, M., Permana, D., Flatau, P., Baranowski, D., Paski, J., Makmur, E., and Sulystyo, E.: On the role of tropical waves triggering extreme rainfall and flood in Sulawesi, Indonesia: a multi-scale interaction perspective, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-310,, 2019

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Presentation version 2 – uploaded on 03 May 2020
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  • CC3: Comment on EGU2020-310, Maria-Carmen Llasat, 04 May 2020

    Thanks for your good presentation Beata, 

    Could you remind me how many of the 49 cases of daily rain accumulation exceeding 100 mm have produced floods? And, the contrary, how many floods have been related with daily rainfalls above 100 mm?

    • AC1: Reply to CC3, Beata Latos, 06 May 2020

      Dear Maria,
      thank you for posting the question. 
      41% of extreme rain events (20 out of 49) have produced floods. In contrary, 51% (20 out of 39) of floods were  associated with extreme rain events.

      • CC4: Reply to AC1, Maria-Carmen Llasat, 07 May 2020

        Thank you very much for your answer, Beata!

Presentation version 1 – uploaded on 30 Apr 2020 , no comments