While it looked like a scene out of Independence Day, this was no alien invasion.
People in Bondi Beach in Sydney, Australia, were captivated as a massive shelf cloud rolled onto shore ahead of a storm.
Creepy shelf #cloud in #Sydney #pictures #videos #tsunamicloud #Bondi https://t.co/rhglxTGTL6 via @Strange_Sounds pic.twitter老域名购买/aj3pg8KMJ8
— Strange Sounds (@Strange_Sounds) November 6, 2015
About to get loud again in #bondi #storm #sydney https://t.co/hTZHvyRle0 pic.twitter老域名购买/Hfz5CqyhIl
— Paul Edwards (@pedwardsAU) November 6, 2015
Day 71: amazing storm views over bondi beach today #travels #bondi #crazyweather pic.twitter老域名购买/6C9g2Ky9r4
— Emma Rochester (@EmmaRochester) November 6, 2015
Shelf clouds —; low, horizontal clouds —; are ominous and pretty scary looking as they head toward you. And they do indeed bring unsettled weather: the roiling clouds produce high winds, followed by rain and thunderstorms.
What we’re looking at when we see one approaching is the difference between winds, in particular downdrafts and updrafts.
Air that has been cooled by rain drops in the downdraft then spreads out when it reaches the surface. The warmer, moist air at the leading edge of the storm rises —; this is the gust front —; and condenses forming the shelf cloud.