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East Coast Lows

The following information was taken from the BOM Climate Education website

Some of the more intense low pressure systems outside the tropics are capable of matching the power and destructive potential of many tropical cyclones.

In a class by themselves in this regard are the class of cyclones known as "east coast lows", which as their name implies, develop near the east coast between southern Queensland and Tasmania.

They are most common off New South Wales, where on average one develops each year, in winter or the transition seasons. Such systems can intensify very rapidly (pressure falls of 24 hPa within 24 hours are not uncommon). They are capable of generating violent gales, at their worst approaching hurricane intensity.

One powerful system in June 1967 was noteworthy for the extensive erosion of Gold Coast beaches. Drawing moisture from the relatively warm waters of the Tasman Sea, these systems can also produce intense, flooding rains; a noteworthy example was the system that brought Sydney to a standstill in August 1986.

East coast lows have in fact been responsible for many of the major flood episodes on east coast river systems - severe flooding in eastern Victoria in June 1998 being a recent example. The systems are a normal part of the climate of eastern Australia, and have been hitting the east coast at least since European settlement. One of the earliest descriptions of an east coast low, in June 1820, can be found in the log book of Captain Phillip King, who charted extensive portions of the Australian coastline between 1818 and 1822.

The Winter storms of June 1967

Occasionally the relative quiet of the Australian subtropics in winter is disturbed by an east coast low, with its gales and flood rains. One particularly severe storm in late June 1950 generated hurricane force winds and 15-metre waves off the New South Wales coast; and the heavily-flooded Clarence River carved out a new path to the sea. In the remarkable month of June 1967, three such storms battered the coastlines of southern Queensland and northern NSW, generating major flooding and extensive erosion of Gold Coast beaches. Six lives were lost.

"Synoptic chart for the storms of late June 1967. The tight gradient indicates very strong winds; the long "fetch" of these strong winds across the oceans off eastern Australia resulted in huge swells that greatly damaged Gold Coast beaches."

The first system developed early in the second week of June, bringing high winds and seas, and torrential rain. On the 11th, a small low pressure centre developed off the Queensland coast, triggering exceptionally heavy rain over Brisbane and surrounds. In 13 hours some 260mm of rain fell, and the 24 hour total of 282mm to 9am on the 12th was Brisbane's heaviest June rainfall ever. Resultant flooding was said to be the worst since 1931. The heavy rains extended several hundred kilometres north and south of Brisbane, with vast areas under water, although flooding extended inland only as far as the fringe of the Darling Downs. The mountainous hinterland of the Gold Coast and northern NSW received exceptional falls, up to 600mm within 24 hours.

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There was to be no respite. The next depression developed off southern Queensland on 21 June, bringing a renewal of strong to gale force southeasterly winds and heavy rain over largely the same areas as before. Rainfall was not so heavy, but falling as it did on saturated soil, it was enough to cause further flooding. Gales and heavy seas lashed the coast between southern Queensland and central NSW. The Gold Coast beachfront, which had been pounded relentlessly through June on top of a summer cyclone season that had extended into April, was by now suffering serious erosion. A third east coast low developed on 26 June, and became notorious for the huge seas it produced. Gale force winds and huge southeasterly swells, generated by an unusually long fetch across the southern Coral Sea, sent mountainous waves crashing onto the crumbling Gold Coast. Houses, buildings, and large sections of roads, undermined by the waves, toppled into the sea. Damage would have been far worse but for the efforts of hundreds of troops and thousands of volunteers who spent days filling sandbags as a bulwark against the huge seas.

Apart from the serious erosion of Gold Coast beaches, June 1967 was noteworthy for the extraordinary rainfall the storms dumped over southeast Queensland and northeast NSW. More than 1,000mm fell over the mountainous hinterland, with 1,631mm at Springbrook. Brisbane's total of 647mm exceeded all but the wettest months in the summer rainy season.