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Warm global temperatures and La Niña

Usually La Niña means colder temperatures but this is a weak one

I figured it was time to review what has been going on with global temperatures over the last few months. Despite El Niño coming to an end earlier this year, the globe still appears to be running a temperature. September came in as the fourth-warmest September on record according to both NOAA and NASA, while October was the fourth warmest October on record according to NOAA and the second warmest according to NASA. The top four warmest Septembers and Octobers globally have all occurred over the last four years. Global satellite measured temperatures for the lowest eight km of the atmosphere, according to the University of Alabama Huntsville, were the warmest on record in both September and October with records going back 39 years.

What makes these values over the last couple of months unusual is the lack of an on-going El Niño event. El Niño years tend to bring warmer global temperatures as the Pacific Ocean releases large amounts of heat into the atmosphere. While it looks like 2017 will end up coming in as the second- or third-warmest year on record, behind 2016 and 2015, it looks like it will be the warmest year ever without any influence from an El Niño.

Never mind El Niño, we need to talk a little bit about La Niña. La Niña, which means the girl or girl child in Spanish, is the opposite condition to El Niño, in that we see colder than average sea surface temperatures across the east-central equatorial Pacific. According to the November monthly advisory issued by NOAA, La Niña conditions are now in place in both the atmosphere and ocean and the odds are around 75 per cent these conditions will continue through to the end of this winter.

So, what does this mean for us? Well, to begin, the current La Niña, so far, is a weak one, which means its overall impact on global weather patterns will typically be less intense. Across our region La Niña typically brings cooler-than-average winter temperatures along with above-average amounts of precipitation. This type of pattern is most persistent over the western prairies and tends to become less persistent as you move eastwards into Manitoba. Since this looks to be a weak La Niña I would say that our current weather pattern has a good chance of being the dominant pattern this winter. Under this pattern we’ll see areas of low pressure cross the prairies every five to seven days. Ahead of these systems we will see mild air move in, followed by a return to cold conditions once the system passes by.

How much snow we’ll see will be determined by where the storm track sets up and how active it will be at any given time. Currently, the storm track is staying to our north, and while we will likely see this track drop southwards at different times, whether or not we will see significant snowfall will depend on whether or not the storm track is active when it is over us. I know that sounds a little wishy-washy, but at this time it is the best I can do. One downside to this possible pattern is that it often favours freezing rain as warm air is pulled northwards ahead of each area of low pressure — something some areas have already had a taste of this winter.

After all of this I decided to take a quick look ahead to see what the latest six-week forecast is calling for, and then what the latest three-month forecast is saying. According to the latest CFS weekly forecast, we should see warmer-than-average temperatures over the next three weeks, followed by cooler-than-average temperatures over the following three weeks. The warmest temperatures are expected over western and extreme southern regions, with near average values over the far north. During weeks 4 to 6 the coldest air is forecasted to remain just to our north, with southern regions running about 1 C to 3 C below average.

The longer range three-month forecast is calling for above average temperatures in December followed by slightly below average temperatures in January and well below average temperatures in February. I will continue to keep an eye on the evolving long-range winter forecasts and will continue to update you on any big changes.

About the author

Co-operator contributor

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.

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