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

Ursa Astronomical Association

Other special clouds - 17.9.2021 at 08.21 Helsinki Observation number 101340

Visibility III / V


4-pronged Kelvin-Helmholtz line in the cloud hole, Helsinki's Hiatalahti. At first I thought / hoped that there would be more of them, but on the contrary (Figure 2), they disintegrated very quickly.


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.

Comments: 5 pcs
Matti Helin - 20.9.2021 at 09.09 Report this

Hienot 

Georg Kieninger - 20.9.2021 at 13.26 Report this

Kiitos kommentista!

Olli Sälevä - 20.9.2021 at 18.35 Report this

Kuinka monta sakaraa tarvitaan, että kyseessä on K-H-pilvi?

Georg Kieninger - 20.9.2021 at 19.47 Report this

Hyvä kysymys johon en osaa kuitenkaan vastata. Olisikohan niin että niiden selväpiirteinen muoto ratkaisee eikä niiden lukumäärä? Tässä tapauksessahan on ehkä vielä sellainen erikoisuus, että ne KH:t syntyivät toisi pieneen pilviaukkoon.

Henrik Heikkinen - 21.9.2021 at 15.44 Report this

Vuoden takaa muistaakseni sakaravaatimus oli 3-5 ellen ole väärässä

 
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