What cloud is that?

The Morning Glory cloud is a roll cloud, or arcus cloud, that can be up to 1,000 km long, 1 to 2 km high and often only 100 to 200 metres above the ground. The southern part of the Gulf of Carpentaria in Northern Australia is the only known location where it can be predicted and observed on a more or less regular basis due to the configuration of land and sea in the area.