Even with the atmosphere still getting its act together over the Pacific, there is still a very good chance that we'll see El Niño conditions develop in the months to come, and have a weak El Niño in full swing by the end of the year.
When word spreads of an El Niño in the works, it's tempting to take this as a promise of a warmer, drier winter, which some would certainly welcome after the bitter cold endured this past winter, but the pattern developing in the equatorial Pacific right now is a little unusual, and it might not deliver on that promise. There are other factors to consider when trying to tell exactly what an El Niño will bring with it (it's never simple is it?), but one of the complications comes from within El Niño itself. Since ocean temperatures rise in two different parts of the ocean due to an El Niño, having one region with higher temperatures than the other changes the outcome.
When there is more warming in the eastern part of the ocean, it results in a more 'classic' El Niño. This pattern is a juggernaut, overwhelming nearly all of the contributions from the other patterns and oscillations that normally have an influence on North American weather. While it holds sway, this type typically results in the generally warmer, drier winter that many Canadians tend to expect from an El Niño. However, when there is more warming in the central Pacific, this produces what's known as an El Niño Modoki - 'modoki' being a Japanese word roughly equivalent to 'almost, but not quite' in English. So, whereas the classic El Niño 'juggernaut' tends to stand alone, the El Niño Modoki is just one 'player' on the field, allowing the other patterns and oscillations to have a greater influence on the weather. The overall effect of this is that, in those El Niño Modoki events, it's harder to know what to expect.
As of this month, forecast models appear to be pointing in that direction again, as the December-January-February forecast from the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) shows:
Credit: JAMSTEC
Indeed, according to University of British Columbia climate scientist Simon Donner, all of the El Niño events seen since the 1997/98 event have been of this 'almost, but not quite' kind.
Notably, 2002-2003 was considered a moderate El Niño Modoki, featuring warm temperatures across B.C. and the prairies during the first few months of 2003, while the eastern half of the country dealt with its longest and coldest winter of the 20 years previous. There were also exceptional events like Atlantic Canada's most expensive rainstorm, and a once-in-a-century ice storm in New Brunswick. The weak El Niño Modoki in 2004-2005 brought a 'Tropical Punch' of warm weather to B.C., while the Prairies were suffering through blizzards and deep freezes and the Maritimes were being buried in snow. In Ontario, the winter seemed like it would never end. Conversely, for 2009-2010 - another moderate El Niño Modoki episode - the warming climate, along with the influences of the Arctic and North Atlantic Oscillations, were all able to exert their influence over that season, producing The Winter that Never Was for many Canadians. However, had the other oscillations pointed in another direction, the situation could have turned out far differently.
What's likely to happen this year? Well, as with the examples above, it's really not easy to tell. Numerous agencies and researchers around the world are monitoring the temperature conditions in the equatorial Pacific and providing regular updates (click here for a look at Environment Canada's latest sea surface temperature anomalies), while we here at The Weather Network are keeping a close eye on the situation as well. Stay tuned to our forecasts and news stories for more updates to come.
(H/T to Dr. Doug Gillham for his invaluable contribution)
