Forecasting the thunderstorm that triggered asthma attacks and killed 10 people in Victoria during a freak event in 2016 is not as straightforward as people think, an inquest has been told.
Seven men and three women, aged 18 to 57, died from asthma after a thunderstorm hit Melbourne on November 21, 2016.
Bureau of Meteorology's Victorian manager Andrew Tupper was the last witness to give evidence at a five-day inquest into the deaths at the Victorian Coroners Court.
The inquest is examining what authorities have learned since high pollen, strong winds, hot temperatures, air moisture and a cold front combined to trigger severe asthma attacks.
Dr Tupper said the bureau had forecast a thunderstorm five days before November 21 and issued a severe thunderstorm warning that day as it monitored changing conditions, including gusts and pollen.
"If you over-warn, you're essentially encouraging the population to not take you seriously," he told the inquest.
"If you under-warn, you're losing confidence that people will be told."
Dr Tupper said there are no statistics available to help them analyse how often high-pollen days combine with thunderstorms to create the same conditions that triggered deadly asthma attacks.
High-pollen days have been known to occur during thunderstorms in Darwin and Sydney, but are a rarer phenomenon in Melbourne.
Other witnesses have told the inquest not all thunderstorms on high pollen days result in thunderstorm asthma.
Dr Tupper also said weather records show places to the west of Melbourne are likely to be hit first with high pollen.
Coroner Paresa Spanos said this suggests areas such as Geelong could give authorities a "forewarning" about weather conditions likely to provoke thunderstorm asthma.
Victims from 2016 were overwhelmingly located in the west and north of Melbourne, when the storm approached from the west.
All 10 victims had asthma and nearly all suffered hay fever, but only three had written asthma action plans.
Ms Spanos has adjourned the inquest until August 24, when counsel for various agencies are expected to make submissions.
