A pilot forecasting system for epidemic thunderstorm asthma in south-eastern Australia

In November 2016, an unprecedented epidemic thunderstorm asthma event inVictoria, Australia, resulted in many thousands of people developing breathing difficulties ina very short period of time, including ten deaths, and created extreme demand across theVictorian health services. To better prepare for future events, a pilot forecasting system forepidemic thunderstorm asthma (ETSA) risk has been developed for Victoria. The system usesa categorical risk-based approach, combining operational forecasting of gusty winds in severethunderstorms with statistical forecasts of high ambient grass pollen concentrations, whichtogether generate the risk of epidemic thunderstorm asthma. This pilot system provides thefirst routine daily epidemic thunderstorm asthma risk forecasting service in the world thatcovers a wide area, and integrates into the health, ambulance and emergency managementsector.Epidemic thunderstorm asthma events have historically occurred infrequently, and noevent of similar magnitude has impacted the Victorian health system since. However, duringthe first three years of the pilot, 2017-2019, two high asthma presentation events and fourmoderately high asthma presentation events were identified from public hospital emergencydepartment records. The ETSA risk forecasts showed skill in discriminating between days withand without health impacts. However, even with hindsight of the actual weather and airbornegrass pollen conditions, some high asthma presentation events occurred in districts that wereassessed as low risk for ETSA, indicating the challenge of predicting this unusual phenomenon