“We urge people to make sure they are prepared.”
Parts of western Sydney were battered with heavy rain and hail with Penrith receiving almost 24mm of rain in half an hour while Canterbury received almost 28 mm in 20 minutes. In Goulburn, about 200 kilometres south of Sydney, 24 mmwas recorded in 30 minutes.
Heavy hail was reported in Mount Druitt while 5cm-wide hail stones were reported at Penrith.
Bureau meteorologist Grace Legge said while storms occurred through much of eastern NSW, Sydney got hit with some of the largest supercells.
“They can be quite isolated… so it can be a little bit hit-and-miss,” she said.
She said the risk of severe thunderstorms still remained as of 9pm but that risk should ease as the night progresses.
The tornado warning was issued just after 4pm when rotation under a supercell was detected on the radar.
“It’s hard to tell on the radar the exact height … but it looks like it didn’t make it all the way down,” Ms Legge said.
Very dangerous thunderstorms were detected near Sydney City, Sydney Airport, Sydney Olympic Park and the Sydney Harbour Bridge at 4.40pm, moving towards the south-east.
The weather bureau issued a warning after a tornado signature was observed over western Sydney at 4.09pm, but by 5:11pm the bureau said the threat of severe thunderstorms had “temporarily eased”.
Earlier, the bureau said very dangerous thunderstorms were detected near Horsley Park, Riverstone and Fairfield.
Very dangerous thunderstorms were forecast to affect Parramatta, Sydney Airport, Sydney Olympic Park and Liverpool by 4:35 pm and Sydney City, the Sydney Harbour Bridge and Randwick by 5:05 pm.
Other severe thunderstorms were detected on the weather radar near Richmond, Newcastle City, Calga, Engadine and Swansea. They were forecast to affect Woy Woy, Waterfall and Budgewoi by 4:35 pm and Gordon, Manly and waters off Stanwell Park by 5:05 pm.
People driving on the M1 between Sydney and the Central Coast were told be “very careful” with a storm cell expected to reach the area before 4.40pm.
A deep cold front associated with a low-pressure system in South Australia is moving across the state and causing severe storms.
The bureau said severe storms were detected at 3.15pm near Wisemans Ferry, Appin, Yengo National Park northwest of St Albans, St Albans and Badgerys Creek. The thunderstorms were moving towards the southeast and were expected to hit Wollongong, Richmond, Campbelltown and Penrith by 3.45pm and Parramatta, Gosford and Mona Vale by 4.15pm.
On Thursday morning, the weather bureau issued a severe thunderstorm warning for Camden, Picton and Campbelltown with predictions of damaging winds and large hailstones.
The storms, which arrived over the Blue Mountains and moved in a south-easterly direction towards Wollongong, passed about midday and the warning was cancelled.
Damaging wind warnings mean gusts over 90km/h were expected. Large hailstones are defined as more than two centimetres in diameter, or the size of a cherry.
During storms the State Emergency Services advises people to secure loose items around the house and move any cars under cover or away from trees.
Weatherzone meteorologist Ben Domensino on Wednesday labelled the weather system the “beast from the south”, warning it would produce a dangerous mix of heavy rain, severe thunderstorms, damaging winds, hail and snow over parts of southern and eastern Australia over the coming days.
More storms are possible on Friday ahead of a fine and sunny weekend in Sydney, the first weekend in four months of eased restrictions when people can legally gather in large groups and visit homes.
Saturday and Sunday are both forecast to reach 23 degrees in Sydney.
The bureau on Wednesday issued a La Nina alert, meaning there is a 70 per cent chance of the weather event occurring in the coming months.