Date
16 December 2017
Hong Kong witnessed a rare meteorological phenomenon on Monday as two large circular holes punched their way through white clouds. Photo: Hong Kong Observatory
Hong Kong witnessed a rare meteorological phenomenon on Monday as two large circular holes punched their way through white clouds. Photo: Hong Kong Observatory

Fallstreak holes whip up excitement

The Hong Kong Observatory (HKO) confirmed that a rare meteorological phenomenon called “fallstreak holes” appeared in Hong Kong skies Monday morning, when two large circular holes were seen in the middle of white clouds, Sky Post reported.

At around 8:30 am, the HKO captured images of the rare sight, which can also be called “rainbow clouds”, resembling a pair of eyes looking down on Hong Kong from the clouds.

According to HKO Scientific Officer Ho Chun-kit, the Monday phenomenon was the most visible such event in recent years, with rainbow colors seen from within the cloud holes due to reflections of sun light.

People living in several districts, including Chai Wan, Sai Kung, Tsing Yi, Diamond Hill, Tuen Mun and even Lamma Island, uploaded pictures of the spectacular sight to social media platforms on Monday.

According to Ho, fallstreak holes are formed when altocumulus cloud sheets or patches of rounded cloud masses at a sub-zero temperature are disturbed by air current movements such as the passing of aircraft.

The disturbance will cause some water droplets to become ice crystals, and the ice crystals will fall off, causing more ice crystals nearby to drop off as well, thus forming the hollow, Ho said.

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