BOM reports SA hit by seven tornadoes on blackout day

Photo: Debbie Prosser

A report by the Bureau of Meteorology has revealed the South Australian blackout was caused by a “tornado outbreak” and wind gusts of up to 260 kilometres.

The September 28 superstorm, which left the entire state in the dark, was the result of several supercells and included at least seven tornados, according to the BOM report.

“Multiple supercell thunderstorms produced damaging to destructive wind gusts, including at least seven tornadoes, very large hailstones and locally intense rainfall,” the report said.

“These supercell thunderstorms and tornadoes impacted the South Australian power network, contributing to a state-wide power outage.”

The 62-page report released by the Bureau of Meteorology said the state was hit by “one of the most significant severe thunderstorm outbreaks in recent decades”.

“The severity of the thunderstorms was aided by an intense and powerful mid-latitude cyclone (low pressure system), which intensified over the Great Australian Bight on 28 September and directly impacted the state on 29 September.”

The report gives a detailed analysis of the severe storms, including a timeline of events.

The Bureau gave four of the seven tornadoes a rating, with three of them rated ‘F2’. This rating estimated 190 to 260km per hour wind gusts.

The fourth was rated ‘F1’ with estimated wind gusts of 127 to 189 kilometres per hour.

The state gets 40 per cent of its power from wind, with all coal-fired generation ceased.

The rest of the power comes from a mix of gas-fired power and two interconnectors linking to Victoria’s brown coal-fired power plants.

The state’s reliance on renewable energy created arguments regarding the cause of the September storm.

The AEMO said in its preliminary report into the statewide blackout that five system faults occurred within 88 seconds, leading to six voltage disturbances.

They reported 13 wind farms online at the time of the storm did not ride through the six voltage disturbances, resulting in 445MW of energy not being generated.