News / Edmonton

La Niña expected to bring longer, colder winter to Edmonton

But one professor warns to be cautious of weather forecasts beyond two weeks

Forecasters are predicting a cold and long winter

Kevin Tuong / Edmonton Freelance

Forecasters are predicting a cold and long winter

Albertans can expect a colder and snowier winter this season, but should probably hold off on buying a plane ticket to Arizona for six months just yet.

John Wilson, a University of Alberta professor who teaches weather analysis and forecasting in the department of earth and atmospheric sciences, said there is currently a weak La Niña weather system in effect, which is based on an observation of sea surface temperatures in the Pacific Ocean.

“So we’ve got a La Niña. Then you ask yourself what are the consequences of having a La Niña? What it tends to be associated with is slightly colder weather for western North America,” Wilson said.

“The consensus of forecasters for this La Niña event, is to continue approximately through to February and April. But it’s a weak event,” he added.

Most of Alberta, Saskatchewan and southern Manitoba are expected to see higher than average precipitation, Wilson said. The Prairies tend to be more acutely affected by La Niña weather systems because of our proximity to the Pacific Ocean.

But Wilson emphasized that it’s extremely hard to forecast the weather beyond two weeks.

“It’s very easy for people to have this idea that we can tell what it’s going to be like a month from now, but we can’t, or we can’t without any reliability,” Wilson said.

Weather forecasts are primarily determined on two methodologies: deterministically and probabilistically.

In the first method, forecasters solve equations based on the fundamentals of physics such as conservation of energy and water vapour in order to make a prediction.

“Those principles get expressed in the form of equations that are solved on a computer in Montreal,” Wilson said.

The other form determines the probability of an event based on statistical averages. An example of this is when the probability of rainfall is included in weather forecasts.

The prediction for higher levels of precipitation for the prairies came from a deterministic forecast, Wilson said.

“Knowing the state of the atmosphere and the ocean on the 31st of October, they ran the model forward in time for three months and averaged its temperature and precipitation patterns,” he explained.

But it’s all subject to change due to the sheer complexity of climatology.

“The historical reliability of that is not very much better than just pure chance. It’s a little bit better, but it’s not very much,” Wilson said.

“You would not want to stake your life on this turning out to be true.”

It’s probably a safe bet to buy winter tires either way, though.

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