Cat risk modelling firm AIR Worldwide has released a comprehensive severe thunderstorm model for Australia that explicitly captures all three sub-perils - hail, tornado, and straight-line wind to help companies assess and manage severe thunderstorm risk.

“In Australia, insurance losses from severe thunderstorms are greater than those from other natural perils such as earthquakes, tropical cyclones, bushfires, or floods,” said Dr. Eric Robinson, manager and principal scientist, AIR Worldwide. “Because aggregate losses from severe thunderstorms can result in extreme volatility in financial results, a robust view of the risk is critical for organisations developing resilience strategies.”

The AIR Severe Thunderstorm Model for Australia simulates daily severe thunderstorm activity based on historical occurrence rates and local and seasonal weather patterns. The daily simulation enables the model to capture both the large outbreaks that produce insured losses in excess of AUD 10 million -- the ICA threshold for a catastrophe -- and smaller events that may last only one day, but that could still impact a company’s portfolio on an aggregate basis, or a more rural portfolio on an occurrence basis.

The AIR model uses historical data from Australia’s Bureau of Meteorology (BOM) Severe Storms Archive, which comprises storm reports from a trained weather spotter network. To compensate for inherent bias from eyewitness reporting of the historical data, AIR employed a hybrid physical-statistical method to simulate hail, straight-line wind, and tornadoes in physically realistic locations, including areas that may not have experienced major activity in the brief historical record. This method blends information about atmospheric conditions conducive to severe thunderstorms with BOM storm reports data, resulting in a spatially complete catalogue of simulated events that offers companies a more accurate view of their severe thunderstorm risk

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