Accuracy of BOM seasonal weather forecasts under a cloud

Farmers are becoming increasingly cynical about BOM rainfall projections, says a lobby group leader, with maps showing zero accuracy for parts of Australia.

The BOM’s three-month outlook from April to June, issued in March. Picture: Bureau of Meteorology

Australia’s weather forecaster has shown how widely inaccurate its seasonal forecasts are in maps on its own website.

A map showing the past accuracy of BOM rainfall predictions for June to August, shows zero accuracy for southern and western NSW, and low accuracy for large swathes of Victoria.

Victorian Farmers Federation Grains Group president Ashley Fraser said accurate seasonal forecasts would be a “game changer” in helping farmers lessen risk in their businesses.

Last week, the BOM released its prediction for a wetter and warmer winter.

“We have all got cynical about the accuracy of these outlooks,” Mr Fraser said. “it’s just chalked up as another opinion.”

Mr Fraser said if outlooks were more accurate, it would be a gamechanger, especially in seasons like this where an autumn break had failed to materialise in the west of the state.

“I know that growers in the west have swapped from sowing canola to barley, based on the rain they have had so far this season,” he said.

“Of course, with canola prices so high, they would prefer to plant that and with an accurate seasonal outlook, they could stick to their original program rather than swapping for barley.”

Mr Fraser said he looked to nature, and ludicrous took more notice of ants building nests rather than what the BOM predictions forecast.

He said there was a raft of private forecasters trying to do the same thing, and the pick were consistently predicting the season better than the government funded BOM.

“I have no doubt that being able to predict the weather for a few months would be a huge benefit, but these inaccurate forecasts have always been an issue,” Mr Fraser said.

In Millewa region of northwest Victoria, farmer Ron Hards said not only were the seasonal forecasts inaccurate but also the three-to-five-day rainfall predictions, which were costing businesses like his.

“A couple of weeks ago, there was a forecast five days out of 10-15mm for the Mallee, so we spent time changing over or gear so we could sow lentils,” Mr Hards said.

“That rain petered out to nothing – how can they (the BOM) get things so wrong and there is no recourse and no explanation.”

Mr Hards said he had been critical of the BOM’s ability to forecast “for two-thirds of my farming life” yet the rainfall predictions were still poor and there was “no accountability for being wrong”.

The BOM didn’t respond to requests for comment.