Tropical Cyclone Savannah has formed just inside the western boundary of Australia's area of responsibility, becoming our fourth named cyclone of the season.

Savannah was located close to 2,200 kilometres away from Western Australia's northwest coast when it became a tropical cyclone on Thursday morning. While it's a long way from Australia's mainland, the system will pass close to Cocos (Keeling) Islands on Thursday.

Image: Tropical Cyclone Savannah to the west of the Cocos (Keeling) Islands on Thursday morning.

A Cyclone Warning has been issued for the Cocos (Keeling) Islands, where wind gusts may reach 100km/h and 30-100mm of rain is possible during Thursday.

Tropical Cyclone Savannah is expected to move south of the Cocos (Keeling) Islands from Friday and then turn towards the west over the weekend. Savannah should head further out into the Indian Ocean during the beginning of next week and is unlikely to affect Australia's mainland directly.

Savannah is the fourth system to form inside Australia's area of responsibility so far this season, following Riley, Penny and Owen.