Mild November pattern defies typical El Niño set-up

Monday, November 2, 2015, 6:46 PM - The first week of November is bringing warm weather that is more typical of late September to parts of eastern Canada including southern Ontario and southern Quebec. Many places will break records this week as high temperatures approach and, even exceed, 20C.

If this forecast holds true, that would make November 2015 rather unusual for a year with a strong El Niño.

While the weekend will bring a return to more seasonal temperatures to this region (preceded by another classic fall storm with strong winds), we do not see signs of persistent cold during the next few weeks.

In fact, much of southern Canada should see temperatures near to above seasonal through at least mid-November. While the Prairies are seeing a taste of winter this week, the chilly temperatures will not here to stay.

As we look back over the past 75 years, most El Nino years had one thing in common – a cold November across much of southern Canada. The map below shows a composite of the November temperature pattern from eight years that had a moderate to strong El Nino (1997, 1982, 1957, 1965, 1972, 1986, 1991, and 2002). The various shades of blue indicate regions that experienced below seasonal temperatures during November of those years.

There are only two El Niño years on record that had a warm November. Those years were 2009 and 1963 but neither of those years had an especially strong El Niño.

So, why the difference this year and what are the implications for this winter?

To help explain this, we need to take a look at the ocean water temperature patterns around the world.

The map below shows our current ocean water temperature pattern, with the various shades of red highlighting the regions that have warmer than normal l ocean water temperatures. The shades of blue indicate areas with colder than normal ocean water temperatures.

The circled area in the Pacific Ocean along the equator west of South America is the region that we pay attention to for El Niño. Warmer-than-normal ocean water temperatures in this region are associated with El Niño and currently ocean water temperatures are currently well above normal.

Let’s see how that compares to 1997, which had the strongest El Niño on record (just slightly stronger than our current El Niño). That year had a very cold November before heading into a mild winter.

While there are some similarities between the two years (1997 on the left vs. 2015 on the right), there are also some key differences. First, in 1997 the water was considerably warmer just west of South America than what we are seeing this year.

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Second, the North Pacific to the west of Canada and the United States is significantly warmer this year than it was in 1997. Also, we see a very different temperature pattern across the Atlantic Ocean between these two years.

Given these differences, it is not a surprise that there are some differences in the associated weather. It may be worth noting that while the cold November of 1997 was followed by a mild December, the El Niño years that had mild Novembers were followed by a much colder pattern during December.

There is no question that the strong El Niño will impact our weather pattern as we head into winter. However, while strong El Niños have the reputation of being associated with mild winters across much of Canada, there certainly are other factors to consider. We continue to see indications that this winter will not mimic the strong El Niño winters of the past (1997-1998 and 1982-1983) and we will continue to take this into consideration as we finalize our winter forecast which will be released on 1 December.