Lightning-packed Supercell over Cheung Chau, Hong Kong

Yesterday evening (30 April 2024), weather monitoring imagery showed an intense rainstorm/thunderstorm area – a “supercell” approaching Hong Kong from the west.

ABUNDANT lightning recorded by HK Observatory

I went from my home to the public pier at the nearby Cheung Chau typhoon shelter, with ideas of taking photos of lightning as the storm approached. Well, that didn’t work out as I hoped – the lightning was then just flashes lighting up rather distant clouds; and soon views were obscured as rain swept in.

The rain became intense, with strong gusts – the Observatory recorded gusts of up to 100km/hr at Cheung Chau, so I opted to stay put in the shelter of the pier, albeit with rain blowing right through it at times. Shot some video of the harbour area, and Praya [waterfront road], with pouring rain, wind, and lightning flashes.

The storm ended even more abruptly than it began, with the sky flashing every few seconds; and I then headed to Tung Wan beach, for some shots of the lightning viewed from the rear of the storm, over Hong Kong Island and Lamma. I’ve compiled the footage into a short film:

Short film as supercell passed over Cheung Chau, Hong Kong; including lightning illuminating the skies over Hong Kong Island and Lamma

Here, a couple of screen grabs from the video footage [edited]:

Anvil crawler – cloud-to-cloud lightning – over Hong Kong Island

In all, there were over 9000 cloud-to-ground lightning strokes recorded by Hong Kong Observatory as the supercell passed; quite many shots on Facebook just now of lightning bolts over the city from this time.

Such an intense storm is unusual for April; but the weather has been unusual lately, with intense heat to the south, such as record temperatures in Hainan, and frequent intense rainstorms including with hail, and even a few tornadoes, in south China – till this, mostly missing Hong Kong.

Really a supercell?

On exTwitter, I’ve had someone query if this was indeed a supercell, which should mean:

Supercells are storms — usually, but not necessarily, thunderstorms — that contain updrafts that rotate about a vertical axis. This rotation is derived from shear in the environmental wind field (that is, a change in wind direction and / or speed with height) surrounding the storm as it begins to grow. Supercells often produce damaging wind, large hail, and tornadoes, and most strong to violent tornadoes are associated with supercells. Analogous to cancer cells in a living organism, supercells differ from ordinary thunderstorms in that the rotation of their updraft enables them to overcome the self-limiting mechanisms that bring demise to regular storms. Once formed, a supercell may perpetuate itself for an appreciable length of time, even upon encountering an environment that is hostile to the development of new storms.
SUPERCELLS by NOAA

Well, I hadn’t checked hard; had been watching this storm on radar for a few hours – so it was persistent; and took “supercell” from a tweet by Jim Yang, a meteorologist with the Chinese Meteorological Association: