Severe weather: a part of Perth’s landscape

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Michael Spencer (CC BY 2.0)

The flooded aftermath of Perth's 2010 hailstorm - one in a long line of destructive weather events.

Rhys Gardiner, Reporter

Wild weather has returned to the news once again as Perth is battered by the last gasps of the cyclone season.

However, it is far from the first time the city has been lashed by the elements.

The remnants of tropical cyclone Mangga passed over the metro area on May 24, causing damage to property and vehicles. Destructive wind gusts were recorded across the state, and more than 60,000 homes suffered power outages.

The Bureau of Meteorology’s severe weather services manager, Bradley Santos, said the system was “somewhat comparable” to an event in June of 2012.

Similar to this year’s storm, “a tropical system interacted with a cold front to produce quite severe wind gusts, particularly over southwest WA,” says Santos.

Aside from ex-tropical cyclone Mangga and the freak thunderstorm in February, the most prominent severe weather event in recent memory is the extensive hailstorm of March 2010. This storm is still WA’s most expensive natural disaster, with the ABC reporting a total of $1.3 billion in insurance claims.

Santos says damaging storms like 2010’s are not normal in the warm season due to Perth’s location.

“We’ve got the ocean to our west, and we’ve got the Darling Scarp to the east – and so often on a warm, hot summer’s day, we’ll get the sea breeze coming in. And often, the storms will develop along that sea breeze,” he says.

Storms usually form over the Perth hills on this sea breeze and track to the southeast, avoiding much of the metro area. Santos says the difference with the March 2010 storms was the direction of their “steering flow” – air flow that pushes them along.

“The typical steering flows are from the northwest […] And the steering flow on that particular day was northerly. So the storms formed in the vicinity of Jurien Bay-Badgingarra, and instead of tracking off to the southeast, just grazing the northeast part of the metro area, they tracked directly south and directly impacted the Perth metro area,” he says.

Perth’s records of severe weather go back to colonial times. The earliest recorded tornado in the Perth area occurred on June 4, 1856, flattening Fremantle Prison’s north boundary wall.

The number of reports of severe weather in WA have increased steadily since the 1970s, but Santos says this is due to better monitoring of weather as technology has improved.

“A lot of severe weather reports prior to the early days, in the 60s, 70s and 80s, actually came from the community. Nowadays we’ve got more automatic weather stations and better remote sensing, so we’re better able to capture the number of events that are occurring,” he says.