Jan. 22, 2019 - Catastrophic floods hit the city of Makassar, the capital and the largest city of the southern province of Sulawesi, Indonesia.
Caused by two types of equatorial wave: Kelvin and Rossby waves. Kelvin waves are caused by the Coriolis Force (the rotation of the earth deflecting moving air towards the equator)
Rossby waves are caused by the rotation of the earth and are generally slow but faster near to the equator. An excellent graphic (although showing northern hemisphere) can be seen at: https://oceanservice.noaa.gov/facts/rossby-wave.html
When these waves hit a coastline, they are deflected away from the equator, northward and southward
The crossing of these waves created monsoon surge that collided with Indonesia creating heavy rainfall and flooding seen in the video. Effects of these events must be prepared for and forecasting is vital: both meteorological events themselves and the human impact.
(via Walker Institute)