Technology & Science

Study says don't count too much on long-range forecasts

A new study questions the accuracy of long-range weather forecasts

When flash flooding hit southeastern Manitoba in June it came as quite a surprise. None of the forecasts in the days leading up to the storm had hinted of such severe weather.

Some homeowners complained about the lack of notice.

The weather also stranded a group of Scouts on a canoe trip.

The Scouts had prepared for the forecasted scattered showers, but had to be rescued when a summer's worth of rain fell within two days.

The kids on Sunday morning were quite wet, quite cool, and with the high winds, it would cause some discomfort with the coldnesss," said Daryl Wright with the Manitoba Council of Scouts Canada.

Three were treated for hypothermia.

Now a survey done by a university professor and his students suggests Environment Canada's long-range forecasts are unreliable much of the time.

A former meteorologist himself, Prof. John Hanesiak had his students conduct a fairly simple test - compare the forecasts for Winnipeg in January and February with what really happened.

"The further you get into the future, the accuracy of the forecast gets lower and lower. We basically wanted to quantify that and see how much more," said Hanesiak.

When it came to temperature Environment Canada's predictions were accurate 72 per cent of the time the same day. But when it forecast five days into the future it was accurate just 13 per cent of the time.

Environment Canada uses computers, without human intervention, to predict the three to five day forecasts in many parts of Canada. It also says forecasting is more accurate now than it was ten years ago.

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