Was it raining hailstones or cotton in Hong Kong? Observatory investigates claims

Videos reportedly showing hail falling in the northern part of Hong Kong on Tuesday night were being verified by the weather forecaster, as some internet users reported the “hailstones” were cotton.

Several videos circulating online showed white pellets dancing in the sky in Yuen Long amid strong winds and torrential rain around 9.30pm on Tuesday, half an hour before the Observatory issued a hail warning.

The Observatory advises residents to seek shelter if they encounter hail. Photo: Handout

The forecaster said hail had been reported in the Pearl River Delta region, including Macau and Zhuhai.

“We noticed some videos of suspected hail in Hong Kong on social media, but they were subject to confirmation by the Observatory,” scientific officer Jennifer Yip Ling said.

Yip added that hail was produced during severe thunderstorms, as stronger updrafts brought water vapour above the freezing layer in a cumulonimbus cloud and formed ice particles.

When updrafts cannot support the weight of the particles, they will fall onto the ground as hail.

“Hail is rare in Hong Kong. Climate change will bring more severe weather events, but the occurrence of hail will depend on the development of strong convection weather,” she said.

Yip advised residents to seek shelter immediately if they encountered hail.

Some internet users who were in the same location where the videos were taken said on social media that the white particles were cotton, not hailstones.

One of the videos was shot outside Tin Hau Temple in Yuen Long’s Dai Shu Ha when residents were celebrating the Tin Hau festival.

Some were seen rushing to seek shelter when a strong wind suddenly blew, carrying rain and many snowlike white particles into the air, but performers appeared to be unfazed by the weather and went on with the procession.

“Some said there was hail in Dai Shu Ha, but that was just cotton blown up by the wind, I was there at the scene and we continued dancing amid the torrential rain and strong wind,” said an internet user, who posted some videos on a Facebook group.

Red kapok trees in Hong Kong bloom from March to April, during which the wind carries seeds wrapped in lightweight, fluffy cotton into the air.

A staff member of the Tin Hau Temple said she did not see any hail last night.

Given that the whole of southern China was hit by adverse weather these days, it was relatively easier to predict the weather, but the exact location of heavy rain or hail was highly random and could not be monitored by equipment, the Observatory’s former assistant director Leung Wing-mo told a radio show on Wednesday.

Authorities can only monitor radar images, but they are not 100 per cent accurate either, he added.

Hong Kong has recorded 43 hail events since 1967, most of which happened between February and May, or July and September.

The city last experienced hail in March and April 2023.



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