Sydney residents have experienced a wild weather event on Thursday afternoon, as a severe thunderstorm brought large hail, heavy rain and flash flooding to parts of the city.

The Bureau of Meteorology (BOM) issued a warning for damaging winds, giant hail and possible tornadoes for Sydney and surrounding areas, as a band of supercell thunderstorms developed over eastern Australia.

Some of the worst affected areas were in Sydney’s west and south-west, where hailstones the size of golf balls pelted down and caused damage to roofs, cars and crops.

Penrith recorded 24mm of rain in two hours, while some suburbs experienced power outages due to fallen trees and power lines.

The State Emergency Service (SES) received more than 100 calls for help, mainly for roof damage and flash flooding. Some cars became trapped by floodwaters in Penrith and had to be rescued by the SES.

The storm also caused chaos at Sydney Airport, where flights were delayed and diverted due to the severe weather conditions.

The BOM said the storm was caused by a low pressure system and a cold front that moved across eastern Australia, creating unstable and humid conditions.

The storm is expected to ease overnight, but more rain and storms are forecast for the next week, with an increased potential for significant rainfall early next week.

The BOM advised people to stay indoors, avoid driving through floodwaters, secure loose items around their homes and follow the advice of emergency services.

The hail storm was reminiscent of the 1999 Sydney hailstorm, which was one of the worst natural disasters in Australian history. The storm dropped an estimated 500,000 tonnes of hailstones in its path, some as large as cricket balls. Insured damages caused by the storm were over A$1.7 billion, with the total damage bill (including uninsured damages) estimated to be around A$2.3 billion.

Many residents and businesses are now facing the daunting task of assessing the damage and lodging insurance claims. The Insurance Council of Australia (ICA) has declared the storm a catastrophe, meaning insurers will prioritise claims from affected policyholders.

The ICA said it had received more than 15,000 claims by Thursday evening, with losses estimated at $125 million. However, it expects these figures to rise significantly in the coming days as more people report the damage.

ICA CEO Rob Whelan said insurers were standing by to help their customers recover from the storm. \”Insurers have mobilised their disaster response specialists to work closely with their customers to assess the damage and process claims,\” he said.

\”The ICA is also liaising with state and local governments, emergency services and other key stakeholders to assist policyholders.\”

Mr Whelan advised policyholders to contact their insurer as soon as possible and follow their advice on how to make a claim. He also warned people to be careful of potential scammers who may offer to repair their property for a fee.

\”If you are approached by someone touting for business, ask for identification and contact your insurer for confirmation before signing any contract,\” he said.