Earlier this month, a cloud tsunami swept across the skies of New South Wales, Australia. Known formally as ashelf cloud, it was spotted by Bondi Beach goers as the enormous, several-kilometer long wave-cloud spanned across the sky. These mighty formations are as dangerous as they are beautiful, known to be accompanied by heavy rainfall, gale-force winds, flash flooding, and large hailstones. Forecaster Christopher Webb offered a brief explanation to The Daily Telegraph as to how clouds such as this are formed:
[The shelf cloud] is created by a cold outflow from a thunderstorm lifting the moist air very abruptly, it is an outflow feature from a thunderstorm. When the rain from the thunderstorm comes vertically down it drags the air with it, it spreads horizontally and forms a gust front, you get the humid air being lifted abruptly from the outflow of the thunderstorm.