Insurers are bracing for a flood of claims after Sydney’s “catastrophic” hailstorm on Thursday, which saw many parts of the city pelted with hail up to 8 centimetres wide.

The Insurance Council of Australia (ICA) has declared the storm a catastrophe and said claims so far had been mostly about damage to motor vehicles, including smashed windscreens.

Residents have also been ringing their insurers about damage to tiled or metal roofs and flooding.

ICA spokesman Campbell Fuller said the financial impact of the storms would be significant.

“It won’t be known for some days, or even several weeks,” he said.

“Residents and businesses are prioritising making their properties safe … and they’ll contact their insurers when they get to it.”

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The Bureau of Meteorology said the storms pelted a widespread area with large hailstones.

At Berowra, on the upper North Shore, there were reports of hail about 8 centimetres wide, while Cabramatta in the south-west and parts of Surry Hills received hail about half that size.

“Giant hailstones, which is hail greater than 5 centimetres, are quite specifically driven in supercell thunderstorms,” meteorologist Jordan Notara said.

“We do get them quite regularly over summer through NSW, but these storm cells redeveloped quite intensely over Sydney specifically.”

The state’s most highly populated area was right in the firing line, worsening the impact.

Mr Fuller said an “insurance catastrophe” was declared due to the extent of the damage, which was evident early in the storms.

“The declaration means insurers are prioritising claims from the hailstorm and they’re endeavouring to help customers as quickly as possible,” he said.

It also means a taskforce has been set up specifically to liaise with emergency services and government bodies.

While the cost of the storms will not be known for some time, Mr Fuller said a catastrophe was declared when the damage bill was likely to be in the tens of millions of dollars or higher.

Mr Fuller said hailstorms were often the biggest natural disasters that hit Australia each year.

In 1999, an infamous Sydney hailstorm caused an estimated insurance loss of $1.7 billion.

Brisbane was also hit by a huge “supercell” storm in 2014, which caused over a billion dollars’ worth of damage.

-ABC