Subseasonal drivers of extreme fire weather in Australia during spring and summer

Subseasonal drivers of extreme fire weather in Australia during spring and summer

Australia has experienced an increase in extreme fire weather over the last few decades. The widespread and devastating impacts of the recent 2018-2019 and 2019-2020 Australian bushfire seasons highlight the importance of understanding climatic factors that contribute to extreme fire danger, including large-scale climate driver activity. We present, for the first time, a subseasonal analysis of the impacts of six important drivers of Australian extreme fire weather in spring and summer, and its representation in the Bureau of Meteorology’s ACCESS-S1 dynamical forecast system. The observed likelihood of extreme fire weather increases over most of Australia in association with El Niño, the positive Indian Ocean Dipole, negative Southern Annular Mode, and low split-flow blocking activity. These increases are most pronounced in SON over the southeast where extreme fire weather is up to three times more likely. Large increases in the likelihood of extreme fire weather also occur over south-eastern Australia when the Madden-Julian Oscillation is active over the eastern tropical Indian Ocean. Using retrospective forecasts at lead times of 2-3 weeks for the period 1990-2012, we show that ACCESS-S1 simulates reasonably well the observed modulation of extreme weekly-mean fire weather by each climate driver. Each driver also plays an important role in providing more accurate predictions for regions where ACCESS-S1 captures the observed connection to extreme fire weather. Our results highlight forecast opportunities that will help with predicting the fire potential across Australia every year and will be very useful to many sectors including fire management, health, and emergency services.