18 February 2019
Buildings along the Victoria Harbour were shrouded by clouds and mist Thursday morning when a heavy rainstorm battered Hong Kong. Photo: HK Observatory
Buildings along the Victoria Harbour were shrouded by clouds and mist Thursday morning when a heavy rainstorm battered Hong Kong. Photo: HK Observatory

Rainstorms cool city, bring spectacular ‘waterfall clouds’

Weather on Friday and the weekend is expected to remain unstable, with occasional showers, according to the Hong Kong Observatory.

Temperatures will range between 23 and 27 degrees, providing some relief after the city recorded its hottest day of the year on Wednesday.

Rains may gradually ease off with sunny intervals over the weekend. On Friday, there is possibility of a few squally thunderstorms. 

Unstable weather and humid air may, nonetheless, provide the ideal setting for “waterfall clouds” near mountain ranges.

On Thursday, the Observatory hoisted this year’s second amber rainstorm signal and a thunder warning. Commuters were caught off guard by sudden downpours, which saw Yuen Long and Tusen Wan record 105 and 85 millimeters of rainfall within two hours respectively.

On Wednesday, which was a public holiday to mark Buddha’s Birthday, temperature rose to 31.3 degrees Celsius in downtown areas, with the apparent temperature, the temperature equivalent perceived outdoors, reaching as high as 37 degrees.

But the city can take a break from the scorching sun as coastal Guangdong and the northern part of the South China Sea are under an active stretch of low pressure, according to the Observatory.

Widespread downburst and thunderstorms will still dominate the Pearl River estuary and the neighboring region. You will need an umbrella before going out.

On Thursday, skyscrapers along the Victoria Harbour were shrouded in a sea of clouds as seen from the Peak.

Many photography connoisseurs were on the move to capture the transient yet breathtaking view of low-hovering waterfall clouds permeating the entire harbor and the mid-slope of mountains on both sides.

Waterfall-like orographic clouds usually form after the passage of a trough of low pressure or in severe convective weather conditions, typically in spring or summer, when moist air is forced upward by mountain.

It cools and condenses into cloud water droplets and will then gradually dissipate on the leeward side of the mountain when temperatures increase in the subsiding air, the Observatory said.

Rainy yet cool days won’t last for long, as Hong Kong is entering the warmest season of the year.

Brace yourself for heat waves next week, something that Hong Kong is known for thanks to its subtropical climate and ubiquitous heat island effect.

Nominal temperature will reach 31 degrees starting from next Wednesday when a southerly airstream with subsiding air takes over the region.

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From the Victoria Peak, the tip of the 118-storey ICC is seen amid torrents of clouds. Photo: HK Observatory

A 2016 file photo shows orographic clouds sliding down the mountain ranges near the Lion Rock like a waterfall. Photo: HK Observatory

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