Tropical Storm Talas, which hit Japan on September 2, is expected to cost between $US150 million ($142 million) to $US600 million ($566 million) in insured losses, according to catastrophe modeller AIR Worldwide.

The modeller says that although the storm was weak when it came ashore, it was “unusually large” with tropical storm force winds extending outwards up to 600km.

“Since Talas was slow-moving, taking a full day to track across Japan – which is almost twice as long as had been forecast – its heavy precipitation was particularly damaging,” it said.

Talas made landfall on Shikoku island, the smallest and least populated of Japan’s four main islands, before crossing the central part of the main island of Honshu, passing near the cities of Kobe, Osaka and Kyoto.

The storm broke Japan’s previous rainfall record and exceeded the yearly average rainfall of Tokyo, causing flooding and mudslides.

The wide-ranging loss estimate should be refined as the damage picture “continues to emerge,” AIR Worldwide said.