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The heat is on: BOM launches heatwave forecasting


Just as a record-breaking heatwave was moving eastwards from Western Australia last week, the Bureau of Meteorology (BOM) launched a trial heatwave forecast service. The forecast shows, up to four days in advance, which areas of Australia can anticipate heatwaves. But are heatwave warnings even necessary for “a sunburnt country” with a history of long, hot summers?

The new forecast system establishes the first official Australian definition of a heatwave; “three days of high maximum and minimum temperatures that is unusual for that location”. It also defines three different heatwave categories:

  • Heatwave – high temperatures, but not so hot that residents of the area are unable to cope.
  • Severe heatwave – vulnerable people, such as the elderly, very young, asthmatic and those with existing medical conditions are at risk of health impacts, including death.
  • Extreme heatwave – considerable risk of health impacts, including death, for many people, especially those mentioned in the previous category, outdoor workers and athletes. Significant disruptions to transport, health care, communication and electricity networks are also likely.

Heatwave forecast systems globally

In developing this system the BOM joins its American and UK counterparts in providing public information about heat waves. The UK Met Office runs a Heat-health watch during the summer months. Like the Australian system, the Met Office classifies heatwaves relatively by using local average temperatures and predicted health impacts. The UK has released an annual heatwave plan since 2004, the year following the extensive heatwaves in Europe that killed over 70,000 people.

The United States’ National Oceanic and Atmospheric Administration (NOAA) operate a heatwave monitoring system that issues ‘excessive heat warnings’. This system is not relative but based on a heat index that determines the apparent temperature using a combination of temperature and humidity. Any single day that exceeds 114 in the heat index, or three days where the index is 105 or higher, triggers an excessive heat warning.

Why does Australia need heatwave warnings?

Australia is a hot, dry country that frequently experiences blistering summers. Do we need a heatwave forecast system? Given the “angry summer” of 2012/13, the new data showing that average temperatures in 2013 were the hottest on record for Australia, and predictions of continued global warming affecting our climate, the answer might be yes. This is mainly because extremely hot conditions can kill vulnerable people (especially the very old). The Australian Government’s State of Australian Cities 2013 notes the seriousness of heat as a killer:

Major heatwaves are Australia’s deadliest natural hazards, particularly for cities. Major heatwaves have caused more deaths since 1890 than bushfires, cyclones, earthquakes, floods and severe storms combined.

During the 2009 Victorian bushfires the heat is estimated to have killed almost 400 people in the state, in addition to the 172 who lost their lives in the fires. Heatwaves also cause significant crop losses as well as affecting livestock, pets and wildlife such as possums, flying foxes and birds. Infrastructure also suffers, as trains are delayed or slowed by buckling tracks. Electricity blackouts may occur, either due to failure of the transmission network or deliberately if electricity demand gets too high (known as load-shedding). High temperatures and winds during heatwaves are also one of the major factors that drive bushfires.

Heatwave forecasts can allow society to prepare for these events. Four Australian states have heatwave plans or guides, the implementation of which would benefit from advanced warning. They are listed below.

There is no national heatwave plan for Australia. In 2011 PriceWaterhouseCoopers (PwC) released Protecting human health and safety during severe and extreme heat events: A national framework. The development of BOM’s heatwave forecast tool and the national definition of a heatwave fulfill two of the four recommendations in the PwC report. A national heatwave plan would be easier to develop now BOM can produce national heatwave forecasting.

Australia is hot, and getting hotter

The Commonwealth Scientific and Industrial Research Organisation (CSIRO), BOM and the Intergovernmental Panel on Climate Change (IPCC) all predict that the number of hot days and heatwaves will increase. At the same time the population of Australia is ageing, increasing the number of people that will become more susceptible to extreme heat. Other factors that contribute to heatwave deaths, such as obesity and social isolation, are also on the rise. By 2050 Australia could experience up to 2000 heatwave deaths a year. If BOM’s pilot heatwave forecast becomes part of the National Warning system it would help everyone prepare for these extreme events.