13 Incredible Arcus Clouds

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  • Image: Jeff Kerr

    Massive shelf cloud over Saskatchewan, tinged orange by the rising sun

    Seeing a shelf cloud, as impressive as it might be, usually means one thing: run for cover!

  • Image: Fir0002

    Like an eyelid gently closing over the landscape – a weak shelf cloud in Swifts Creek, Victoria, Australia

    Like most forbearers of bad weather, what we see from below is just the tip of the iceberg, as shelf clouds are attached to a much larger cloud system, usually bringing thunderstorms or cold fronts.

  • Image: Bidgee

    Nothing gentle here – a shelf cloud enveloping the Australian town of Wagga Wagga before bringing a thunderstorm

    Roll clouds, on the other hand, are the gentle giants of the cloud world.

  • Image: Chesnok

    Composition in pink and blue – a shelf cloud bringing Moscow turbulent weather

    Arcus cloud is the term used for a low, horizontal cloud formation associated with thunderstorm or cold front outflows. The two types of arcus clouds are shelf clouds and roll clouds; as their names might suggest they are vastly different in appearance and generation.

  • Image: John Kerstholt

    Parting the skies – shelf cloud over Enschede, Netherlands

    Shelf clouds are attached to their parent cloud, usually a thunderstorm-bringing cumulonimbus cloud.

  • Image: Longyester

    Here, a quite similar divide into good/bad weather zone

    Unlike wall clouds, the cloud phenomenon they are often confused with, shelf clouds bring the storm along while wall clouds appear at the end of it.

  • Image: Pierre cb

    This shelf cloud diagram shows with blue arrows how the cold air descending from a cumulonimbus meets the warm and moist air in the environment (red arrows). Because the cold pool is denser, the warmer, moist air is forced upward and its humidity condenses into a shelf cloud.

  • Image: Arnold Paul

    Shelf cloud over the Baltic Sea close to Øland, Sweden

    In this image, the snaking shelf cloud looks almost ethereal in nature.

  • Image: Dariusz Wierzbicki

    Is that an eagle’s face? Shelf cloud over Warsaw

    Roll clouds are just as amazing a cloud phenomena. Unlike shelf clouds, they are completely detached from their parent cumulonimbus cloud. And unlike wall clouds, they are not liable to morph into tornadoes. Phew!

  • Image: Daniela Mirner Eberl

    Textbook roll cloud over Las Olas Beach in Maldonado, Uruguay

    Long cloud formations like roll clouds are rare as they require uniform cloud formation along an extended front.

  • Image: Dan Bush

    Impressive roll cloud stretching over the fields of Albany, MO and into the horizon

    Roll clouds also usually form near advancing cold fronts whose downdraft causes moist warm air to rise, then cool below its dew point and thus form a cloud.

  • Image: Sensenmann

    Like a giant plantain? Roll cloud over a beach in Yucatan, Mexico

    A bit of a cloud aberration is the Morning Glory cloud, an extremely long and rare roll cloud that has so far only been observed over Northern Australia’s Gulf of Carpentaria, the Mexican Sea of Cortez and Nova Scotia. It can reach a length of up to 1000 km and a height of 1 to 2 km.

  • Image: Daniel Schwen

    Even cars speeding on Germany’s autobahn can’t escape this roll cloud

    Often accompanied by sudden gusts of wind, the Morning Glory cloud can move at speeds of up to 60 km/h. Strong sea breezes and high humidity seem to further the formation of a Morning Glory cloud but despite being extensively studied, this meteorological phenomenon is not yet clearly understood.

  • Image: Mick Petroff

    Triple roll cloud or morning glory cloud over Queensland, Australia

    We could be staring at clouds all day but, well, enough of cloud gazing and back to work.

    Sources: 1, 2, 3

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Simone Preuss
Simone Preuss
Scribol Staff
Science
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