Estimation of Tropical Cyclone Wind Hazard for Darwin: Comparison with Two Other Locations and the Australian Wind-Loading Code

Abstract

The passage of three Australian Category 5 cyclones within 350 km of Darwin (Northern Territory), Australia, during the last decade indicates that that city should have a high wind hazard. In this paper, the wind hazard for Darwin was compared with that for Port Hedland (Western Australia) and Townsville (Queensland) using data from a coupled ocean?atmosphere simulation model and from historical and satellite-era records of tropical cyclones. According to the authoritative statement on wind hazard in Australia, Darwin?s wind hazard is the same as Townsville?s but both locations? hazards are much less than that of Port Hedland. However, three different estimates in this study indicate that Darwin?s wind hazard at the long return periods relevant to engineering requirements is higher than for both Port Hedland and Townsville. The discrepancy with previous studies may result from the inadequate cyclone records in the low-latitude north of Australia, from accumulated errors from estimates of wind speeds from wind fields and wind?pressure relationships, and from inappropriate extrapolations of short-period records based on assumed probability distributions. It is concluded that the current wind-hazard zoning of northern Australia seriously underestimates the hazard near Darwin and that coupled ocean?atmosphere simulation models could contribute to its revision.