Sub-synoptic-scale features associated with extreme surface gusts during the South Australia storm of September 2016 – part I: characteristics of the event

Winds are one of the major meteorological contributors to deaths, damage and insured losses in Australia. A ‘freak storm’ hit the state of South Australia on 28 September 2016, causing state‐wide blackouts and leaving 1.7 million people without power. In the first part of this two‐part study, we analyse this event and find that it was indeed extreme, deepening more explosively than all but two Adelaide‐affecting extratropical cyclones over the past 37 years and exhibiting the lowest central pressure. This generated hurricane force winds, with the central South Australia site of Neptune Island recording a gust of over 120kmh⁻¹. We show that this storm potentially contained a sting jet. Such jets are well known as a cause of major damage across Europe, and this is the first study which investigates whether a sting jet can be produced over Australia. The main deepening of the system occurred over the Great Australian Bight, so if a sting jet did form and make it to the surface, it was not the cause of the state‐wide damage. However, the cyclone did contain numerous extreme gust‐producing mesoscale features, as explored in part II of this paper (Earl and Simmons, 2018).