On 10th April, tropical cyclones Seroja and Odette merged together - a rare phenomenon called the Fujiwhara Effect, which presents a significant challenge in forecasting track and intensity of the tropical cyclones.
Typically, the stronger storm absorbs the weaker storm, and in this case Odette was absorbed by the stronger Seroja, before Seroja made landfall in Australia on 11th April as a category 3 tropical cyclone. The merging of the two cyclones was predicted in ECMWF's forecasts from ~3 days ahead.
Satellite images from NASA's Worldview show the storm(s) on 9th, 10th and 11th April as they merge and make landfall:
