photo #8111877

The gigantic wavelike feature at the front of this Cumulonimbus storm cloud towering over Darwin, Northern Territory, Australia was a welcome sign to Shirley Hendy (Member 45,123). It meant the long-awaited monsoon was beginning.The ridge at the front base of the mighty Cumulonimbus is called an arcus, named with the Latin for an ‘arch’ rather than a wave because it often has a more arched appearance. Forming just ahead of the storm cloud’s downpours, an arcus like Shirley’s can herald the arrival of cool winds and heavy rain. ‘Our late monsoon,’ she said, ‘had finally arrived.’