How does the epidemic thunderstorm asthma forecasting system work?
Epidemic thunderstorm asthma is thought to be caused by high grass pollen levels in the air and a certain type of thunderstorm.
The forecasting system requires a number of environmental and meteorological data inputs related to pollen and weather. Weather conditions associated with epidemic thunderstorm asthma includes wind changes and strong gusts typically observed with thunderstorms. This information comes from the Bureau of Meteorology's numerical weather models and weather forecasters monitoring the most recent weather observations.
Pollen forecasts are dependent on many factors including wind, temperature, rainfall, relative humidity and satellite-estimated grass coverage and condition. The current pollen forecasting model uses information about pollen counts collected over many years in Melbourne. Following the November 2016 epidemic thunderstorm asthma event, the Victorian Government purchased five new pollen monitors (known as "pollen traps"), which are now located across Victoria. This will greatly increase our understanding of pollen distribution across the state. These new pollen counts will also help us to verify and refine the pollen forecasting model.
The system estimates the risk of an epidemic thunderstorm asthma event for the current day, the next day, and the day after that.
The system delivers daily epidemic thunderstorm asthma forecasts from 1 October through to 31 December, the typical Victorian grass pollen season.
How accurate is the epidemic thunderstorm asthma forecasting system?
The science of epidemic thunderstorm asthma forecasting is new and as with all forecasts, there is an element of uncertainty. The epidemic thunderstorm asthma forecast is based on a synthesis of the modelled grass pollen forecast combined with the forecast for a particular type of thunderstorm. These complex models have multiple inputs, including from satellite data and land-based measurements. Its accuracy is limited by how precisely these complex phenomena can be observed and modelled.
Epidemic thunderstorm asthma events are relatively rare, and therefore, it may take some time until the accuracy can be measured with high confidence. Testing the system on past events, we expect the accuracy of epidemic thunderstorm asthma forecasts may be close to that of severe thunderstorm warnings.
The department is also investing in research to better understand the mechanisms of epidemic thunderstorm asthma and increase our forecasting capability in the future.
Where are the pollen traps located in Victoria?
The Victorian pollen monitoring network comprises eight pollen traps at the following locations:
- Waurn Ponds (Geelong)
- Creswick (near Ballarat)
- Dookie (near Shepparton)
- Churchill (near Morwell)
Where can I find data from pollen traps in my area?
In Victoria, the University of Melbourne and Deakin University operate the pollen monitoring network.
As part of the epidemic thunderstorm asthma forecasting system, the Victorian Government is funding the University of Melbourne and Deakin University to monitor grass pollen during the grass pollen season. Pollen information is provided to the Bureau of Meteorology to inform the epidemic thunderstorm asthma forecast, and to the public for personal use.
The University of Melbourne and its partner organisations operate six pollen monitoring sites at Hamilton, Creswick, Bendigo, Dookie, Churchill and Parkville. Information from these sites is available from the Melbourne Pollen mobile app (download from the App Store for iOS devices or Google Play for Android devices) and Melbourne Pollen website.
Deakin AIRwatch provides daily pollen forecasts at Deakin University's Melbourne (Burwood) and Geelong (Waurn Ponds) campuses. Information from these sites is available at the Deakin AIRwatch website.
Why is grass pollen only counted between 1 October and 31 December?
Plants release their pollen when they are flowering, and different types of plants flower at different times of year. Many deciduous trees such as birch, plane and elm flower in late winter and early spring, for example, whereas many grasses flower in the period from October to December.
Research shows that grass pollen is by far the most common cause of spring hay fever (seasonal allergic rhinitis) in Victoria.
Grass pollen data collected in Melbourne for more than 20 years shows that the highest levels start occurring, on average, in mid-October and fluctuate daily until the end of December. By the end of November grasses start dying off and the levels of grass pollen in the air begin to reduce. The exact start and finish of grass pollen season varies slightly from season to season, but is typically from 1 October to the end of December.
The specific grass that is thought to be involved in epidemic thunderstorm asthma events in Victoria is rye grass.
How is a grass pollen forecast different from an epidemic thunderstorm asthma forecast?
Grass pollen forecasts simply reflect the expected amount of grass pollen in the air. They can help people with hay fever (seasonal allergic rhinitis) to prepare for these days. Epidemic thunderstorm asthma forecasts combine grass pollen forecasts with the prediction of a certain type of thunderstorm, thought to produce an epidemic thunderstorm asthma event.
How will I know when an epidemic thunderstorm asthma event may happen?
Epidemic thunderstorm asthma forecasts will be publicly available throughout the Victorian grass pollen season (1 October to 31 December) on the VicEmergency website and app (download from the App Store for iOS devices or Google Play for Android devices).
The forecasts are updated twice daily to ensure that the forecast includes the most up-to-date storm and pollen information. The forecast for the current day will be updated at approximately 12:30pm each day, and the forecasts for the subsequent two days are updated around 3:00pm.
Forecasts will also be used to trigger public advice and warnings on the VicEmergency warnings platform.
How can I access the three-day epidemic thunderstorm asthma forecast?
You can access the three-day forecast on the VicEmergency website or app, or on the Melbourne Pollen website and app, or on the Health.Vic website.