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Ursa Astronomical Association

Other special clouds - 17.8.2014 at 11.30 Turku Observation number 29174

Visibility Unclassified


This cloud combination looked really special here in Turku too, it was a bit difficult to estimate that scale, I put it around now.


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

      Fallstreak hole (Hole punch cloud) is a rare phenomenon observed in cloud cover.

      Altocumulus clouds consist mainly of subcooled cloud droplets, which can be well below freezing, but which have not yet frozen in the absence of suitable freezing cores.

      When freezing nuclei, such as small ice crystals, come into contact with the cloud, the droplets of clouds may begin to freeze outward from this point so that an annular opening appears to form in the cloud. Such an opening is called a hole cloud.

      One source of freezing cores may be airplanes that create a cloud of holes as they pass through the altocumulus layer. Hole clouds can also be oblong in shape when the aircraft has flown a little longer at cloud height. In this case, ice crystals floating down from the opening remains in its path. In the middle of these openings or canals, a thin line of ice crystals, or Virga, visible below the cloud layer, can typically be seen. If the sun happens to be at a suitable distance from this rain line, a halo phenomenon, such as a side sun, can be detected in the wake.

      A hole cloud formed in the Altocumulus layer with a rain line of ice crystals, or Virga, in the middle. Image by Jari Luomanen.

Comments: 4 pcs
Jouni Hovi - 17.8.2014 at 17.27 Report this

Taitavat olla karkaavat kiteet tuossa keskellä putoilemassa... hienoa että löysit tämän myöskin. Ei liene tuon vasemmalla olevan jättövanan tekeleitä siis.

Paula Mattila - 17.8.2014 at 17.33 Report this

Ei,se oli kyllä aivan eri kohdassa,mutta vanan varjo näkyi hienosti pilven pinnassa.

Matti Helin - 17.8.2014 at 17.45 Report this

Näkyihän se Turussakin. Jännä perspektiivihämäys tuon koneen jättövanan kanssa. Liedosta katsottuna se näkyi reiän sisäpuolella. 

Matti Helin - 17.8.2014 at 18.12 Report this

Omalla havaintopaikalla arvioin reiän läpimitaksi suunnilleen 80-90 astetta. 

Noista meidän kuvista voisi joku noheva tehdä 3D - mallinnuksen :) 

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