Winter is coming. Will El Nino keep it warm?

Even by northern standards, the last two winters, especially in the N.W.T., have been cold. Very cold.

Last year, some regions saw their harshest winter in decades, with temperatures dropping into the 30s for months without relief. In Yellowknife, for example, there were 10 days below 40 Cand more than 20 days below 30C degrees. Temperatures averaged around fiveto 10 degrees below normal, especially in December and February. Although the Yukon and Nunavut saw close to normal temperatures last winter, daily highs still remained in the 20sfor weeks on end in those areas.

So, will this year be any better? Perhaps, thanks partly to a phenomenon called El Nino.

El Nino occurs when the waters of the Eastern Pacific off the coast of South America are warmer than normal. Under normal conditions, the ocean waters are warmer in the western Pacific than in the east, and winds travel in a conveyor belt pattern: rising over Indonesia bringing rain, travelling eastward at high levels, sinking in the eastern Pacific and returning back towards the west at low levels.

In an El Nino year, this conveyor belt system weakens, causing drier conditions in the western Pacific, and more rain over the central or eastern Pacific. This in turn can disrupt weather patterns around the world.

Earlier this year, signs of an El Nino have appeared with warmer than normal waters in the East Pacific. Although the probability of an El Nino event has decreased over the past few months, officials with the U.S. National Oceanic and Atmospheric Administration believe it could still happen.

If it does, there could be drastic effects on the North American winter.

In an El Nino year, warmer sea temperatures in the southern Pacific mean stronger upper atmospheric winds in the North Pacific. This causes more intense low pressure systems developing in the Gulf of Alaska, which in turn drives more unseasonably warm air into Western Canada, including the North.

There have been a number of El Nino events in the past decade, with weak El Ninos reported in the 2004/2005, 2006/2007, and 2009/2010 winters. In February of 2010, temperatures in the North were around 7 C above normal. To put this in perspective, average daily highs in Yellowknife for the month of February in 2010 were around 12.3 C.

But El Nino is only one of the factors affecting northern winter temperatures. According to David Phillips, Environment Canadas senior climatologist, winters in the North are already warmer than they used to be, due to climate change, and El Nino events, like all weather forecasts, can be difficult to predict with complete accuracy.

Still, Phillips models are indicating warmer than normal temperatures in the Western Arctic through the months of November, December, and January. Lets hope.