Key Takeaways
- A rapidly deepening “bombing low” southwest of Western Australia is generating damaging to locally destructive winds, heavy rain, and hazardous surf across the state’s southwest, including Perth.
- Wind gusts exceeding 125 km/h are possible south of a line from Lancelin to Albany, with observed gusts up to 117 km/h at Cape Leeuwin.
- Rainfall totals of 15–50 mm have been widespread, with several locations recording their highest May daily totals in years; intense 10‑minute bursts reached 12 mm at Perth Stadium.
- Coastal hazards include abnormally high tides, damaging surf, and potential erosion along exposed sections of the WA coast.
- The system is expected to move away from WA by Monday, then traverse eastward, bringing wintry weather, strong winds, showers, thunderstorms, and alpine snow to South Australia, Victoria, Tasmania, and New South Wales later in the week.
Overview of the Bombing Low’s Development
The low pressure system that formed southwest of Western Australia has undergone explosive cyclogenesis, a process meteorologists term a “bombing low.” Between Saturday morning and Sunday morning its central pressure dropped by roughly 25 hPa, far exceeding the 16–17 hPa threshold needed for bomb classification at latitudes 35–37°S. This rapid deepening was fueled by a combination of an intense upper‑level jet stream, unusually warm sea‑surface temperatures off parts of the WA coastline, and a cold pool aloft that sharpened the horizontal temperature gradient. The resulting pressure gradient has driven strong, gusty winds across a broad swath of the state’s southwest.
Wind Hazards and Observed Gusts
Damaging to locally destructive winds are the most immediate threat from the system. Forecasts indicate gusts in excess of 125 km/h are possible south of a line from Lancelin to Albany, encompassing the Perth metropolitan area. Observations up to 06:00 WST Sunday confirm the severity: Cape Leeuwin recorded a peak gust of 117 km/h at 05:40 WST, while Cape Naturaliste reached 104 km/h at 06:00 WST. Other notable stations included Busselton Jetty (98 km/h), Garden Island HSF (89 km/h), North Island (87 km/h), Mandurah and Swanbourne (both 85 km/h), Dwellingup (85 km/h the previous evening), Geraldton Airport (83 km/h), and Gooseberry Hill (82 km/h). These values underscore the potential for structural damage, fallen trees, and power outages across the affected region.
Rainfall Impacts and Record‑Breaking Totals
Accompanying the strong winds, the bombing low has delivered substantial rainfall to southwest WA. Since 09:00 WST Saturday, widespread falls of 15–50 mm have been recorded, with several localities experiencing locally higher amounts. Notable 24‑hour totals (to 05:30 WST Sunday) include Busselton Airport at 50.6 mm—its highest May daily total in eight years—and Manjimup at 43.6 mm, the highest in 21 years. North Island logged 31.2 mm (25‑year May record), Bridgetown 27.0 mm (six‑year record), Geraldton Airport 26.6 mm (five‑year record), and Cunderdin Airport 23.4 mm (27‑year record). These figures illustrate both the breadth and intensity of the precipitation associated with the system.
Intense Short‑Duration Rainfall Bursts
In addition to steady rain, the system produced intense, short‑lived downpours. Ten‑minute rainfall data revealed extreme rates, particularly around Perth Stadium, where 7.0 mm fell in ten minutes at 00:50 WST Sunday, followed by 12.0 mm in the next ten‑minute interval at 01:00 WST Sunday. Busselton experienced multiple bursts exceeding 5 mm per ten minutes during the late evening of Saturday, while Manjimup Shire recorded 5.6 mm in ten minutes at 23:30 WST Saturday. Such rapid rainfall can lead to flash flooding, overwhelmed drainage systems, and hazardous driving conditions, especially in urban areas with limited infiltration capacity.
Coastal Hazards and Surf Conditions
The bombing low’s influence extends to the marine environment, generating coastal hazard warnings for abnormally high tides and damaging surf along parts of the WA coastline. The combination of strong onshore winds and low pressure has elevated sea levels, increasing the risk of coastal inundation and erosion, particularly on exposed beaches and cliffs. Surf heights are expected to be significantly above normal, posing dangers to swimmers, boaters, and coastal infrastructure. Authorities advise the public to heed beach closures, avoid rock fishing, and secure loose items near the shoreline to mitigate damage from wave action and potential storm surge.
Forecast Evolution and Movement of the Low
Meteorological models indicate the bombing low will begin to move away from Western Australia during Monday, with the strongest winds gradually subsiding over the southern coast as the system departs. After exiting WA, the low is projected to track eastward across southern Australia, bringing a spell of wintry weather to South Australia, Victoria, Tasmania, and New South Wales later in the week. This downstream evolution is expected to include strong to damaging winds, heavy showers, isolated thunderstorms, and alpine snow in elevated regions. Residents in those states should monitor updates and prepare for potentially disruptive conditions as the system advances.
Preparedness and Safety Recommendations
Given the multifaceted threats posed by this bombing low—destructive winds, heavy rainfall, flash flooding, and hazardous surf—residents and businesses across southwest WA should take precautionary actions now. Secure outdoor objects, reinforce windows and doors where possible, and avoid unnecessary travel, especially in areas prone to fallen trees or power lines. Stay informed through official sources such as the Bureau of Meteorology, local emergency services, and road authority updates. If flash flooding is possible, avoid low‑lying roads and watercourses, and be prepared to evacuate if advised. For coastal communities, heed beach closures, avoid rock fishing, and secure vessels and equipment against strong surf and possible surge.
Broader Implications for Weather Patterns
The explosive development of this bombing low highlights the dynamic nature of mid‑latitude cyclones in the Southern Hemisphere, particularly when favorable upper‑level jet dynamics interact with anomalously warm ocean waters and cold air aloft. Such systems can rapidly intensify, producing extreme weather over large areas and influencing downstream patterns for several days. The anticipated eastward progression of the low underscores how a single intense system can cascade into a series of weather impacts across multiple states, affecting agriculture, transport, energy demand, and emergency management resources. Continued monitoring and improved modeling of these rapid intensification events remain crucial for enhancing forecast accuracy and community resilience.