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Skywarden,
Ursa Astronomical Association
Kopernikuksentie 1
00130 Helsinki
taivaanvahti(at)ursa.fi

Ursa Astronomical Association

Other special clouds - 21.4.2021 at 16.50 Kouvola, liikkala Observation number 97887

Visibility III / V


Cold, rain and wind coming. I would suggest the Kelvin-Helmholtz clouds when I found something similar. In this way, in hindsight, I could not have taken a broader picture for comparison ...


Additional information
  • Havainto
    • Other special clouds
  • Cloud coverage in the sky
    • Very small area
  • Other special clouds
    • Kelvin-Helmholtz cloud info

      The Kelvin-Helmholtz clouds are among the most exotic apparitions in the cloud world.

      They resemble regular waves in shape, typically several in succession. String wave strings are created at the top of the cloud mass when there are layers of air moving at different speeds in the air.

      If there is moisture in one layer of air, it may rise into waves in another layer of air moving at different speeds. There is Kelvin-Helmholtz instability between the air layers at that time, from which the cloud waves are named.

      Waves in lakes and seas are the result of this same instability between layers moving at different speeds. Kelvin-Helmholtz waves can also be seen in the gas circles of Jupiter and Saturn, for example.

      Only clearly wavy cases can be called Kelvin-Helmholtz clouds. It is good to be careful not to confuse them with conventional undulatus clouds. The cloud types can be difficult to identify, especially when viewed from the side.

      In a real Kelvin-Helmholtz cloud, the wave structure is clear. Only well-developed and undisputed Kelvin-Helmholtz clouds are collected to the Sky Watch database.

      Wavy Kelvin-Helmholz clouds. Image Grahamuk / Wikipedia.

      Tom Eklund observed these Kelvin-Helmholtz clouds in Finland.

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