Water spout forms on the Brisbane River as supercell thunderstorm ...

A water spout has momentarily appeared on the Brisbane River today after a severe but short-lived supercell swept across the city.

Bureau of Meteorology senior forecaster Shane Kennedy told ABC Radio Brisbane it was an extremely rare and "exciting" weather phenomenon.

"It's a bit of a weak water spout across the river lasting for a handful of seconds, possibly up to half a minute," he said.

"They're pretty rare; often we'll get some more erratic swirling winds associated with a thunderstorm but you often can't see them.

"It looks like we got lots of good footage of it from different angles, so pretty exciting to see."

The afternoon storm from the Brisbane suburb of Annerley.  (Supplied: Katelnd Griffin)

He said this particular water spout appeared to be a weak whirlwind, but was not quite strong enough to be classified as a tornado.

He said water spouts were caused by strong downdrafts forming into a swirling vortex pattern, sucking up water as it went.

Large hailstones that fell at Greenslopes. (Supplied: Fletcher Gibson)

Mr Kennedy said the severe thunderstorms were continuing to track north across the coast, but the worst of the weather should be over.

He said the storms had brought hail about three to four centimetres in length, but the it should have largely subsided.

Queensland Ambulance Service (QAS) said a 22-year-old man had suffered ankle and head injuries after being hit by a falling tree branch at the bottom of Kangaroo Point cliffs.

A 22-year-old man was injured after being hit by a fallen tree branch at Kangaroo Point cliffs.  (ABC News: Dean Caton)

It comes after reports the water spout had uprooted a tree at the top of Kangaroo Point cliffs, causing it to fall to the bottom.

The QAS spokesperson said the man was in a stable condition.

Student Li Mengtong was caught in the storm near the water spout while out for a walk along Kangaroo Point.

Li Mengtong was out for a walk when the storm hit. (ABC News: Dean Caton)

With trees and branches falling around him, he said he was forced to hold on to a railing to avoid being blown over.

Mr Mengtong said he was lucky to be saved by two nearby workers who called him over to their car.

"These two people saved me, they saved my life," he told the ABC.

BOM has labelled the weather system a "supercell". (Supplied: Katelnd Griffin)

ABC Radio Brisbane listener, Michelle from South Bank, said she was astonished when she looked out of her balcony and saw the towering vortex.

"We looked towards the Kangaroo Point cliffs and there was this huge water spout picking up leaves and water and everything," Michelle said.

"Then it caught a tree on the top of Kangaroo Point cliffs and half of it fell to the bottom.

"Then this massive rainbow appeared, so we had rain, hail, sun, rainbow, and a water spout."

Brisbane Airport is experiencing delays after the storm, but there have been no reports of damage to the terminal or aircraft.

"There was a short burst of small hail, as the severe cell dropped a rapid 7mm of rain, before sunshine quickly returned," airport spokesperson Peter Doherty said.

"As a precaution, engineers are conducting inspections of aircraft to ensure there's no hail damage, before clearing them for flight."

"Departures are experiencing an average 50-minute delay, with arriving flights an average 30 minutes behind schedule."