Bombing low hammers southwest WA as fierce winds worsen

A bombing low southwest of WA is now impacting broad areas of the state’s southwest, with conditions expected to worsen through Sunday. Severe weather warnings are current across southwest WA during Sunday for damaging to locally destructive winds, while coastal hazard warnings are in place for abnormally high tides and damaging surf along parts of the WA coast. Locally destructive gusts in excess of 125 km/h are possible southwest of a line from Lancelin to Albany, including Perth, during Sunday.

As we wrote yesterday, this system has undergone explosive cyclogenesis, with models showing the low’s central pressure falling by an average of about 25 hPa in the 24 hours from Saturday morning to Sunday morning. This is well above the roughly 16 to 17 hPa threshold needed for a bombing low near 35–37°S. The system has several powerful ingredients, including an intense upper level jet, abnormally warm waters off parts of WA and a cold pool aloft helping create a sharp temperature contrast.

Image. 6-hour Himawari visible satellite loop showing the bombing low spinning southwest of WA.

Heavy showers, isolated thunderstorms and significant winds are expected to continue across the southwest, including Perth, with conditions likely to worsen this afternoon and evening as the low and its associated cold front move through. Damaging surf may also cause coastal erosion and localised damage along exposed parts of the WA coast.

The strongest WA wind gusts observed in the supplied data up to about 6am WST Sunday include:

Cape Leeuwin: 117 km/h at 5:40am WST;

Cape Naturaliste: 104 km/h at 6:00am WST;

Busselton Jetty: 98 km/h at 3:04am WST;

Garden Island HSF: 89 km/h at 6:00am WST;

North Island: 87 km/h at 4:12am WST;

Mandurah: 85 km/h at 5:30am WST;

Swanbourne: 85 km/h at 2:08am WST;

Dwellingup: 85 km/h at 9:30pm WST Saturday;

Geraldton Airport: 83 km/h at 5:19am WST;

Gooseberry Hill: 82 km/h at 1:07am WST.

Rain has also been significant, with widespread falls of about 15 to 50 mm and locally higher totals in parts of WA since 9am Saturday to early Sunday morning. Notable rainfall totals since 9am Saturday include:

Busselton Airport: 50.6 mm to 5:30am WST Sunday, its highest May daily total in 8 years;

Manjimup: 43.6 mm to 5:30am WST Sunday, its highest May daily total in 21 years;

North Island: 31.2 mm to 5:30am WST Sunday, its highest May daily total in 25 years;

Bridgetown: 27.0 mm to 5:30am WST Sunday, its highest May daily total in 6 years;

Geraldton Airport: 26.6 mm to 5:30am WST Sunday, its highest May daily total in 5 years;

Cunderdin Airport: 23.4 mm to 5:30am WST Sunday, its highest May daily total in 27 years.

Intense bursts of rain have also been recorded, with 10-minute rainfall data showing the following WA rates:

Perth / Perth Stadium: 7.0 mm in 10 minutes at 12:50am WST Sunday;

Perth / Perth Stadium: 12.0 mm in 10 minutes at 1:00am WST Sunday;

Busselton: 6.2 mm in 10 minutes at 9:50pm WST Saturday;

Busselton: 6.0 mm in 10 minutes at 10:20pm WST Saturday;

Busselton: 5.2 mm in 10 minutes at 10:00pm WST Saturday.

Manjimup Shire: 5.6 mm in 10 minutes at 11:30pm WST Saturday;

The low should move away from WA during Monday, with the last of the strong winds likely affecting the southern coast. After that, the system will march east and bring a spell of wintry weather to SA, Vic, Tas and NSW through the late this week, including strong to damaging winds, heavy showers, isolated thunderstorms and alpine snow. Please stay up to date with the latest warnings as this system continues to unfold.