Heavy swells

The powerful winds that accompany tropical cyclones and east coast lows can and do generate huge waves. If these waves are not intercepted by land areas, they may traverse hundreds, even thousands of kilometres of ocean as large, long swells. Thus huge waves generated by far distant storms occasionally pound the coastlines of Australia, even during otherwise fine, settled weather conditions. In May 1999, storm-force winds associated with an intense low pressure system about 1000 kilometres off eastern Australia generated eight- and nine-metre high swell-waves that pounded a thousand kilometres of the Queensland and New South Wales coastlines, causing injuries and beach erosion on the Gold Coast. While east coast lows closer to the coast have generated larger waves and produced more damage (see, e.g., article on "the winter storms of June 1967"), the arrival of such huge waves during otherwise settled conditions is a spectacular feature of our climate.

Along the southern coastline, many large swells are generated well south of the continent by strong westerly gales that can blow unimpeded for thousands of kilometres. Moving north away from their source region, they may arrive as huge swells, often with little warning. On the south and west coasts of Tasmania stormy conditions are not unusual, but one particular event stands out - for its magnitude, and for the suddenness and unexpectedness of its onset.

On 26 August 1982, a light to moderate westerly wind was blowing over Tasmania, and seas were slight - hardly the conditions for monster waves. Yet those whose business took them near Tasmania’s south coast that day observed a rapid and spectacular increase in southwesterly swell waves in the late morning and afternoon. By mid-afternoon enormous waves - as high as 15 metres - crashed on to the beaches and rocks lining the rugged coast between Maatsuyker Island and the Tasman Peninsula. Waves moved up Frederick Henry Bay and swept over the beach at Lauderdale (washing most of it away). Even within the sheltered canal at Lauderdale, the waves still possessed enough power to damage boat ramps and sheds.

Having peaked in the afternoon, the swells declined substantially over the next few hours, and by next day, little trace remained except for the battered structures and scoured beaches. The event took no lives and affected few people: yet the arrival of such large and potentially destructive waves from a far-off source remains an intriguing feature of our climate, and one with obvious practical significance for marine and coastal operations.