Damien rapidly strengthening as it tracks toward northwest Australian coast

Maura Kelly

As Damien continues to intensify over open water, forecasters say the severe tropical cyclone will unleash flooding rainfall and damaging winds over Australia's Pilbara coast this weekend.

This storm started as a broad area of low pressure in a swath of tropical moisture over northern Australia earlier this week, where rounds of tropical downpours increased the risk for flash flooding.

This satellite image shows Tropical Cyclone Damien nearing the northwestern coast of Australia on Saturday morning, local time. (Photo/CIRA RAMMB)

Late in the day on Wednesday, the storm moved over the Timor Sea and into an environment more conducive for tropical development.

The storm quickly developed into a Category 1 tropical cyclone and was given the name Damien by the Australian Bureau of Meteorology (BOM). This is equivalent to a tropical storm in the Atlantic and East Pacific basins. As of Friday afternoon local time, Damien strengthened into a Category 3 severe tropical cyclone on the BOM scale.

Warm waters and an area of low wind shear will support further strengthening as the cyclone begins to turn toward the south and southeast over the Timor Sea.

Damien is forecast to be a Category 4 severe tropical cyclone as it moves inland over the the Pilbara coast of Western Australia on Saturday, local time. At this strength, Damien will be the equivalent of a strong Category 3 or Category 4 hurricane in the Atlantic.

"Damaging winds, coastal flooding and rough surf look to be most likely between Onslow and Wallal Downs late Friday night and Saturday, local time," said AccuWeather Senior Meteorologist Jason Nicholls.

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As the storm approaches the coast, winds can gust to around 240 kph (150 mph) near and just east of the center of the storm.

Downed trees and power lines can lead to power outages and damage to structures, especially in these areas. This will also lead to dangerous surf and coastal flooding due to the strong onshore flow.

Heavy rainfall will also be a concern into the weekend as the storm pushes inland. Widespread rainfall totals of 100-200 mm (4-8 inches) are likely near and along the track of the storm.

An AccuWeather Local StormMax™ of 400 mm (16 inches) is possible in areas that receive prolonged periods of heavy rain. These areas will also be at the greatest risk for major flooding.

"There may even be a risk for impacts to natural gas and oil production as Damien moves through the area," added Nicholls. "A number of gas and liquid processing facilities will be in the path of the storm."

Farther inland, winds will begin to weaken rapidly through Saturday night and into Sunday as the storm interacts with land, but occasional downpours will still be likely.

By the beginning of next week, Damien is forecast to weaken to a tropical rainstorm and bring showers and thunderstorms to parts of Western Australia as the storm drifts south.

Localized flooding is possible in central and southern parts of Western Australia that receive any heavy rain.

The system is expected to continue to weaken before dissipating over the Great Australian Bight into the middle of next week.

Keep checking back on AccuWeather.com for the latest updates on this storm and your forecast.