Dec. 20 (Bloomberg) -- Tropical Cyclone Billy crossed Australia’s far northwest coast, bringing gale-force winds and potentially heavy rainfall, the nation’s weather bureau said.

The category one storm was estimated to be 70 kilometers (44 miles) north-northwest of Wyndham and 235 kilometers east of Mitchell Plateau, moving west at 4 kilometers an hours in Western Australia state, at 9 a.m. local time, the Bureau of Meteorology said on its Web site.

“Gales with gusts to 100 kilometers per hour are currently being experienced between Kalumburu and the Northern Territory- Western Australia border,” the forecaster said. “They are expected to persist for the next 6 hours then gradually ease.”

Australia’s northwest, the site of most of the nation’s oil and gas output, may have more tropical cyclones than average this season, potentially threatening operations, the bureau said in October. The region may have five to seven cyclones from Nov. 1 to April 30, up from four last year, it said then.

Woodside Petroleum Ltd. and Royal Dutch Shell Plc were among oil companies that suspended drilling exploration or appraisal wells in the Browse Basin on Dec. 16 and evacuated workers because of the possibility of a cyclone forming.

Tropical Cyclone Billy hasn’t caused any major damage so far, the Australian Broadcasting Corp. said, citing Western Australia’s State Emergency Services.

Weakening

“The cyclone is expected to weaken into a tropical low later today as it continues to move inland, but may redevelop into a tropical cyclone on Monday if it moves off the west Kimberley coast, causing gales between Kalumburu and Beagle Bay,” the bureau said.

Widespread heavy rainfall is likely over the southern Darwin-Daly district, the northern Victoria River district and parts of the Kimberley. There may be significant stream rises and local flooding in those areas, extending west into the north Kimberley later, the forecaster said.

The bureau will release its next cyclone update at 1:30 p.m. local time.

To contact the reporter on this story: Madelene Pearson in Melbourne on mpearson1@bloomberg.net

Last Updated: December 19, 2008 21:12 EST