Twisters in the Land Down Under

January 07, 2016

Any conversation about Australia's major natural hazards will likely include cyclones, floods, bushfires, hail, and even, on occasion, earthquakes. Many forget to consider tornadoes, given that they are a rarer phenomenon in Australia. When they do occur, they are usually of lower intensity than many of those observed in the U.S. Nevertheless, the tornado that ripped through the southern Sydney suburb of Kurnell on December 17, 2015, serves as a stark reminder that these events have the potential to cause significant damage if they strike populated areas.

Categorized as an F2 (Fujita scale) tornado, the peak wind gust was recorded at the Kurnell Automatic Weather Station as 213 km/h. This wind speed was the highest ever recorded in New South Wales (NSW), the previous record being the 171 km/h logged at Nobby's Beach in Newcastle in May, 1974. Although Australian tornadoes rarely exceed F2, tornadoes this powerful can cause considerable damage, tearing roofs off structures, wrecking manufactured homes, toppling trees, lifting cars off the ground, and turning debris into missiles that can exacerbate the destruction.

The Australian Bureau of Meteorology notes that, "tornadoes occur more commonly in NSW than most people would expect." Its database lists 364 tornadoes recorded between 1795 and June 2003 across the state. Most are reported in late spring and summer (October−March), but they can strike at any time of year; while they usually happen in the afternoon, the Kurnell tornado struck in the late morning.

One of the most significant tornadoes to impact Australia rampaged through the suburbs of Brisbane, the capital of Queensland, in November 1973. In terms of damage, this is considered to be the worst Australia has ever seen because a powerful tornado passed through a major metropolitan area. The length of its track―from Brookfield to Victoria Point―was about 51 km and its width ranged from 100−230 m. It damaged about 1,400 buildings, of which about 500 lost their roofs and 500 were declared structurally unsafe.

Tornadoes may not be the most frequent hazard in Australia, but they do have the potential to cause significant damage. The Insurance Council of Australia (ICA) declared the recent Kurnell tornado a catastrophe and estimated insured losses of around AUD 10 million. This event may not be particularly significant in terms of estimated incurred losses, but it is a timely wake-up call. To help insurers assess their tornado risk, AIR is developing a severe thunderstorm model for Australia, which will explicitly model tornadoes (along with hail and straight-line wind) and account for their potential losses.

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