Reply

A reexamination of the wind hazard from tropical cyclones for the city of Darwin (Northern Territory), Australia, by Cook and Nicholls concluded that its wind hazard is substantially underestimated by its allocation to region C in the Australian wind code. This conclusion was dismissed by Harper et al. on the basis of interpretation of anemometer records and Dvorak central pressure estimates as well as criticism of the simple technique and data used to interpret historic records. Of the 44 years of historical anemometer records presented by Harper et al. for Darwin, however, only one record was for a direct hit by an intense tropical cyclone. The other records derive from distant and/or weak tropical cyclones, which are not applicable to understanding the wind hazard at long return periods. The Dvorak central pressure estimates from which Harper et al. conclude that Port Hedland (Western Australia), Australia, has a greater wind hazard than Darwin does, when back transformed to Dvorak current-intensity values and gust speeds, indicate the converse. The simple technique used to derive wind hazard from historical cyclone occurrence is defended in detail and shown to produce estimates of wind hazard that are close to those accepted for five locations on the hurricane-affected coastline of the U.S. mainland. Thus the criticisms by Harper et al. of Cook and Nicholl’s work are shown to be invalid and the original conclusion that Darwin’s wind hazard is substantially underestimated in the current Australian wind code is supported.