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

Ursa Astronomical Association

Other special clouds - 20.9.2021 at 14.39 - 20.9.2021 at 14.40 Raisio Observation number 101347

Visibility III / V


A pretty "banana" swirled on a windy afternoon at the front edge of a cloudberry. It was in the order of more than a minute from the moment of detection, so I only recovered the handset images. It looked very turbulent at the height of the clouds, lifted several flags of some kind to the front edge, but I no longer saw any similar structure.


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

      A horseshoe vortex cloud occurs when an upward flow in the atmosphere collides with a horizontally moving air mass. This may cause a horizontally rotating vortex. If moisture condenses in the vortex into cloud droplets, a very rare upside-down U-shaped cloud shape can be observed. Often such a vortex is only visible for a very short time, perhaps a few tens of seconds or minutes.

      Typically, horseshoe clouds are said to be visible in the vicinity of supercellular storms, as they are associated with very strong upflows and wind torsions that are conducive to the formation of a vortex. Yet this cloud shape is observed just in conjunction with conventional Cumulus clouds and sometimes even very far from them against a completely blue sky. To detect this cloud, you should therefore be careful whenever cumulus cloud is generated as a result of upflows.

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