Losses from Tropical Cyclone Ilsa could have reached into the billions of dollars if the system had taken a different path, highlighting the sensitivity of damage impacts to the exact track of severe storms, Risk Frontiers says.

Ilsa reached category five strength on April 13 as it neared Port Hedland in WA and broke the record for highest sustained winds for storms making landfall in Australia, with 218 km/h observed on Bedout Island. But the cyclone came ashore along a sparsely populated part of the Pilbara coastline.

The destruction of the Pardoo Roadhouse, 100km east of Port Hedland was the only significant damage reported, while port activities were put on hold for just 24 hours.

Risk Frontiers says early loss estimates based on cyclone modelling indicate total financial damage likely ranges from $4-26 million.

Cyclone Rusty was the last event to hit Port Hedland, before making landfall at the same location as Ilsa in 2013 as a category 3. Its slow-moving approach resulted in 39 hours of gale force winds and very high rainfall, causing the evacuation of 26 ships and 330 residents, prolonged airport and port closures and power losses for 3000 householders.

Early loss estimates for Rusty totalled $10 million, excluding lost revenue from impacts such as an 86-hour port closure, which was estimated to cost $500 million.

Risk Frontiers says an ensemble of track maps similar to Ilsa indicates a median total loss of about $10 million, but one track is “a clear outlier with a total loss in the order of billions of dollars”. In that scenario, the cyclone reaches category five strength just 30km from Port Hedland before moving toward Pardoo.

“The relatively small losses observed in the wake of TC Ilsa highlight the importance of storm tracking over storm intensity for estimating potential damage,” the report by Risk Scientist Maxime Marin and Senior Research Scientist Lucinda Coates says.

“TC Ilsa marks the (likely) end of a below average tropical cyclone season activity with a reminder that even in the context of decreased frequency, Australian communities remain highly vulnerable to tropical cyclones, whose damage can vary exponentially depending on their eventual paths.”