Tasmanian Heat Wave History and Forecasting

HEAT WAVES AND HEALTH Heat waves, in Australia, may be responsible for more deaths than any other natural hazard (Coates 1996), with over 4,000 fatalities recorded up to the year 1990, with particularly high death rates for the elderly, infirm, and outdoor workers. Heat waves can also have wide-spread impacts on infrastructure, such as failure of electrical power systems and transport. Australia can be expected to experience more frequent/intense heat waves in the future (Alexander et al 2007), with both the mean, and the extremes of temperature showing an increasing trend. In Tasmania in particular, climate projections point to warmer night-time temperatures, doubling to tripling of the number of summer days with temperatures greater than 25ºC, and lengthening of the summer period into autumn and spring, and an overall increase in the frequency of heat wave occurrence (ACE CRC 2010). Numerical forecast models are good at predicting temperatures from the slow-moving weather systems that drive heat waves (Nairn & Fawcett 2013), so there is potential for accurate warning systems of extreme heat events to be established. A variety of heat wave indicators, some based on single days, others on three-day means, some including humidity or based apparent temperature have been utilized in the past. Most are based on temperature exceeding a set threshold for a period – the length of the period, and the threshold used varies between jurisdictions based on local knowledge of heat effects. The EHF index, (Nairn & Fawcett 2013) provides a standard, globally applicable metric of extreme heat event intensity, taking into account local acclimatization to temperature, recent conditions, and total heat load. The ability to gain a measure of the intensity of heat wave have events is important, given the increasing effects of greater heat load on human health and infrastructure.