THE freak storm that hit Melbourne two weeks ago is on track to be one of the 10 most costly Australian natural disasters of the past 50 years, according to insurance experts.

The Insurance Council of Australia say that insurers have so far received 79,000 claims worth $491 million, but industry experts predict that figure will go past $700 million.

If so, it will surpass the $707 million figure - in 2007 dollars - set by a hailstorm in Sydney in 1986, currently the 10th most expensive insurance event since records began in 1967. It is already Victoria's costliest storm. Only bushfires, specifically Ash Wednesday and Black Saturday, have cost the state's insurers more.

''We're still taking claims, and that figure's looking to rise,'' said council spokeswoman Sandra Van Dijk.

''The Melbourne situation happened in two hours. That's rare. In two hours we declared it a catastrophe and for it to be declared a catastrophe it has to meet a number of guidelines … off the top of my head I don't know of any other storm in Melbourne in recent memory [that's caused that much damage].''