Advice: East coast lows explained

The reason? Australia is currently under the influence of an east coast low, an intense low-pressure system that creates some of the most dangerous coastal conditions we will ever experience, with very rough seas and prolonged heavy swells.

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How dangerous? Think about the disastrous 1998 Sydney Hobart yacht race where the entire fleet was smashed, and the bulk carrier the Pasha Bulka that grounded spectacularly near Newcastle in 2007.

East coast lows are always bad news for boaties. The one we’re experiencing now has prompted a number of warnings from authorities as reports flood in of boats breaking moorings and running aground, and even sinking.

NSW Maritime executive director Mark Hutchings said boat owners needed to take extra care in extreme weather to ensure boats were securely moored, as they would be responsible for any damage their loose boat may cause.

“Winds can cause vessels to break free of their mooring tackle, the rain can fill bilges and debris can entangle mooring lines, cause damage and become hazards to safe navigation,” Hutchings said.

Adding to the problems are power failures, which can also lead to a spike in the number of boats sinking at their moorings as on-board batteries struggle to keep up with the demands of running bilge pumps to drain the rainwater flooding bilges.

Not only that, but heavy rains wash debris into waterways, which can tangle with moorings, block cooling water intakes, and become a hazard to boats moving about on the water.

NSW Marine has urged boaters to avoid non-essential boating on flood-affected waterways until a clean-up from the wild weather has been carried out.

According to the Australian Bureau of Meteorology, we cop about 10 east coast lows a year, with most happening in the middle of the year. Of these, usually one will be a bad one similar to the one we’re experiencing right now.

These lows are usually the tail end of tropical cyclones that sweep into Australia, generating winds ranging anywhere from gale force (around 60-70km/h) to storm force (around 90-100km/h) winds, although they have been known to peak at 165km/h.

Accompanying the wind is rain. These result in flash flooding in the short term, and more widespread flooding as river systems struggle to cope with the volume of water inundating them – some Sydney suburbs are reporting more than 150mm of rainfall in a 24-hour period.

Adding to the runoff problem are the bushfires that have swept the eastern coastline since late last year; with a lack of ground cover enhancing erosion and huge volumes of bushfire debris washing into waterways and, ultimately, out to sea.

Combined with the strong onshore winds, the east coast low is also resulting in coastal inundation as the storm surge, waves of up to 10 metres off Sydney and strong onshore winds push water onto low-lying land, with disastrous results for some property owners. A spring tide – meaning it will have the biggest difference between low and high tide – is due today.

Gale force winds are expected to continue to hit Australia’s eastern seaboard today, with conditions easing to strong wind warnings tomorrow.