Weather How accurate are weather forecasts? BoM defends Melbourne storm warnings

How accurate are weather forecasts? BoM defends Melbourne storm warnings

A person is seen crossing Bourke Street in Melbourne's CDB on Saturday, Photo: AAP
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The Bureau of Meteorology has been forced to defend its forecasts of a south-east coast soaking after huge rainfall hit parts of Victoria later than anticipated, prompting residents to question whether it would arrive at all.

More than a century of daily record rainfall totals were smashed in Victoria’s north and northeast with more than 123mm of rain in Echuca near the border of New South Wales and 146mm in Euroa on Saturday.

The rainfall spawned floodwaters, evacuation warnings and SES rescues with several people trapped in their vehicles.

Parts of New South Wales are also now expected to cop a drenching in the Snowy Mountains, south coast and central west.

The wild weather had already struck South Australia, where storms on Thursday night caused more than 3700 homes to lose power across the state. Adelaide received a reprieve from the deluge, but more rain is expected in the next few days.

However, the biblical-level storm feared by forecasters bypassed Melbourne and other major cities that had battened down the hatches on Thursday and Friday.

The Bureau of Meteorology issued severe weather warnings on Thursday for Melbourne – estimating 150 millimetres of rain between Friday and Sunday.

In a first for Victoria, about 7.4 million SMS messages were sent to mobile devices on Friday and Saturday saying “flooding is expected” and to check on family and friends.

Preparations began on Thursday afternoon with major event cancellations including the Great Victorian Bike Ride and the Taste of Melbourne, while many employees were sent home from work early fearing flash flooding.

But as Melbourne braced for the worst, the city received a total of 21 millimetres on Friday and Saturday. Other suburbs in the north and east of the city recorded 30 to 50mm, including 80mm in Healesville.

Many frustrated residents took to social media using the hashtag ‘#melbournestorm’ to vent their frustration about the bureau’s strong weather messages.

“Who is the hype man for BoM? He needs a raise,” one Twitter user joked on Saturday.

Another post said, “This storm is disappointing. I just wanted a little bit of catastrophe.”

Victorian weather bureau manager Dr Andrew Tupper defended the severe weather warnings at a press conference on Saturday morning.

“If we had our time again, yes, we would have put out an event with similar language to that,” Dr Tupper said.

Dr Tupper likened significant rainfall events to cyclones or an upcoming bushfire event.

He said forecasters could understand the potential and severity of the event before knowing “exactly where that event is going to hit”.

“That’s why we went out very hard before the event because we could see that it was certainly going to be a large and impactful event,” he said.

When questioned if residents could become desensitised or untrustworthy of such weather warnings in future, Dr Tupper said “there was always that risk”.

“I’m quite satisfied that the event is pretty much as we described – it’s just a bit of a bonus that Melbourne itself hasn’t been impacted as much.”

A 2007 study assessing the accuracy of Melbourne forecasts found incorrect forecasts of significant rain events still remained a major forecasting problem.

The report titled The Accuracy of weather forecasts for MelbourneHarvey Stern of the BoM said despite improved techniques for data assimilation, better satellite information and improvements to numerical weather predictions had not improved public weather forecasts.

 – With AAP

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