Queensland bushfires 2018

Mingzhu Wang, Lucinda Coates and Thomas Mortlock.

In 2018, Queensland had the third-warmest spring and forth-warmest November on record, in terms of mean temperature (BoM, 2018d). At the end of November, exceptional heat affected eastern Queensland, with some locations reaching their highest annual maximum temperatures ever recorded. Wildfires raged across central Queensland and more than 140 fires were burning throughout the State during the last week of November (BoM, 2018d), due to a combination of the prolonged heatwave and other “unprecedented” conditions. More than a million hectares have been burnt out, with 15 dwellings and more than 60 sheds or other structures being reported as damaged (Caldwell, 2018). Given the human population in the affected area, casualties were light: one man died after being hit by a falling tree while clearing a firebreak at Rolleston in the Central Highlands. All the threatening fires were contained by 5 December, with weather conditions easing due to severe storms sweeping across Queensland. Figure 1 shows all the fire hotspots for Queensland from 26 November to 5 December.

Figure 1. Recorded fire hotspots derived from VIIRS imagery for Queensland from 26 November to 5 December. Data Source: Geoscience Australia (2018)

Record-breaking heatwave and catastrophic fire risk

Extreme heatwave conditions started developing in far north Queensland from 23 November 2018, and then spread across the north-east and central regions of the State (Figure 2). This heatwave was unusual as the temperatures were 5-10 °C above the November average, the humidity was exceptionally low for this time of year and the extreme hot conditions extended over a much longer period than “usual” heatwaves. The above-average temperature and unseasonally dry and hot westerly winds led to severe to locally extreme fire danger over large parts of eastern Queensland. The fire danger conditions peaked on 28 November, reaching a catastrophic level for the Capricornia, Central Highlands and Coalfields regions (Figure 3). Cairns hit 42 °C two days (27 & 28 November) in a row, which are the hottest days on record for the region in November.

Figure 2. Three-day heatwave assessment from 27 November to 29 November. Source: BoM (2018b)
Figure 3. Fire danger rating map for Queensland on 28 November. Source: BoM_QLD (2018)

According to Phoenix fire simulation technology (Figure 4), about 8,000 residents needed to be evacuated from Gracemere, west of Rockhampton. The town was subsequently saved, using a combination of water bombing aircraft and fire-fighting crews on the ground. Another significant bushfire originating in the Deepwater National Park on the central Queensland coast burnt out more than 17,000 hectares and forced hundreds of people to evacuate (Figure 5). This Deepwater blaze was extremely dangerous due to erratic wind direction changes, high fuel loads and low humidity, having a 66-kilometre perimeter and flames up to 10 metres in height (Ferrier et al., 2018).

Figure 4. The predicted fire burning pathways through Gracemere. Source: Doman (2018)
Figure 5. False colour Sentinel 2 image showing the burnt areas in black at Deepwater on 26 November. Source: Sentinel Hub (2018)

Comparison with previous bushfire events in Queensland in Risk Frontiers’ natural hazards database (PerilAUS) show that bushfire events around Brisbane, in 1994, also occurred after a heatwave. However, no event in PerilAUS has ever covered such a vast expanse of Queensland as this recent one. And there have been relatively few properties lost in any previous fires.

Connected systems

As discussed in our Briefing Note 381, a heavy rain event on 28 November affected the Illawarra, Sydney Metropolitan and Central Coast areas in New South Wales. At the same time, Queensland was suffering extreme heatwave and fire danger conditions (Figure 6). Sarah Fitton of BoM indicated these two contrasting events were driven by connected systems (Doyle, 2018). Figure 7 shows that the abnormal westerly flow to the north of the low was responsible for the catastrophic fire danger ratings along the tropical QLD coast and it extended down into the low-pressure system across the New South Wales south coast. The two events were linked and influencing each other. The low over New South Wales was pushing warm air and stronger winds to Queensland through the connected system, intensifying fire danger conditions (Yeo, 2018).

Figure 6. Australian daily maximum & minimum temperature & rainfall extreme area maps on 28 November. Source: BoM (2018a)
Figure 7. The connected low-pressure systems that drove the heavy rain event in New South Wales and Queensland catastrophic fire conditions on 28 November. Source: BoM (2018c)

Conclusions

When considering these recent fire events in Queensland, it is clear that the catastrophic fire risk is substantially influenced by record extreme weather events. Clarke et al. (2012) has shown increased fire weather conditions in Australia since the 1970s. Unprecedented conditions may become a new normal and peril factors correlating together can worsen local situations.

Risk Frontiers is currently building a new bushfire model using the latest remote sensing technologies and machine learning models. This model, along with Risk Frontiers’ loss models for other meteorological disasters, will soon be correlated on the Multi-Peril Workbench to better price cascading hazards.

References

Bureau of Meteorology [BoM] (2018a), Australian daily maximum temperature extreme area maps, available at http://www.bom.gov.au/cgi-bin/climate/extremes/extreme_maps.cgi, accessed 08/12/18.

Bureau of Meteorology [BoM] (2018b), Heatwave Service for Australia, available at http://www.bom.gov.au/australia/heatwave/, accessed 27/11/18.

Bureau of Meteorology [BoM] (2018c), Latest colour mean sea-level pressure analysis, available at http://www.bom.gov.au/australia/charts/synoptic_col.shtml, accessed 29/11/18.

Bureau of Meteorology [BoM] (2018d), Queensland in November 2018: Exceptional heat along the east coast at the end of the month, available at http://www.bom.gov.au/climate/current/month/qld/summary.shtml, accessed 08/12/18.

Bureau of Meteorology, Queensland [BoM_QLD] (2018), Fire Danger Rating, available at https://pbs.twimg.com/media/DtEJBfxX4AMVgg-.jpg, accessed 27/11/18.

Caldwell, F. (2018), Almost $1 million in hardship grants paid to bushfire victims, The Sydney Morning Herald, available at https://www.smh.com.au/politics/queensland/almost-1-million-in-hardship-grants-paid-to-bushfire-victims-20181205-p50kes.html?ref=rss&utm_medium=rss&utm_source=rss_feed, accessed 08/12/18.

Clarke, H., Lucas, C., & Smith, P. (2012), Changes in Australian fire weather between 1973 and 2010. International Journal of Climatology, 33(4), 931-944

Doman, M. (2018), From space, the ferocity of Queensland’s bushfires is revealed, ABC, available at https://www.abc.net.au/news/2018-12-08/from-space,-the-ferocity-of-queenslands-bushfires-is-revealed/10594662, accessed 08/12/18.

Doyle, K. (2018), Sydney weather and Queensland bushfire extremes have a common thread, ABC, available at https://www.abc.net.au/news/2018-11-28/sydney-weather-and-queensland-bushfires-linked/10561792, accessed 08/12/18.

Ferrier, T., Layt, S., & Kohlbacher, S. (2018), The Australian, available at https://www.theaustralian.com.au/news/latest-news/locals-flee-as-qld-blaze-threatens-homes/news-story/ea2cf27bd8aa724b380d71177bf7fc6c, accessed 08/12/18.

Geoscience Australia (2018), Historic Hotspot data, available at https://sentinel.ga.gov.au/#/, accessed 08/12/18.

Sentinel Hub (2018), EO Browser, available at https://apps.sentinel-hub.com/eo-browser/?lat=-24.2823&lng=151.7881&zoom=11&time=2018-11-26&preset=2_FALSE_COLOR&datasource=Sentinel-2%20L1C, accessed 08/12/18.

Yeo, C. (2018), Sydney storms could be making the Queensland fires worse, The Conversation, available at https://theconversation.com/sydney-storms-could-be-making-the-queensland-fires-worse-107789, accessed 08/12/18.