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How will the transition from a strong El Niño to La Niña impact our weather this summer? Find out what you can expect for the next several months when The Weather Network releases their summer forecast on Tuesday, May 24 at 9:00 pm EDT.

Summer Preview 2016: Curtain pulled back on next 3 months

Visit this Summer Forecast Guide to the Season for the 2016 Summer Forecast, Summer Weather Preview and much more.


Dr. Doug Gillham
Meteorologist, PhD

Tuesday, May 24, 2016, 7:25 PM - How will the transition from a strong El Niño to La Niña impact our weather this summer? Find out what you can expect for the next several months when The Weather Network releases its summer forecast on Tuesday, May 24 at 9:00 pm ET.

However, before we get to the summer forecast, we need to take a look back and answer the question that many have been asking.

What happened to the warm spring that you forecast?

The spring forecast verified very well in western Canada and in Newfoundland, but residents of Ontario and Quebec have good reason to be asking the above question.

The map on the left shows our spring forecast while the map on the right shows temperature patterns through mid-May.

It likely comes as a surprise to most in southern Ontario that the spring as a whole has been very close to seasonal in this region – not warm, but not as cold as it has seemed. This is because March was actually very warm. However, April and May turned colder than normal across this region and while May will end warm across this area, it will be too little, too late.

So, what happened?

During the past several months we have been in the midst of a transition from one of the strongest El Niño events on record to what will likely be a strong La Niña. Making this transition in the global pattern while also transitioning from winter to summer was bound to lead to some tumultuous weather patterns.

One of the key surprises in this transition was having the atmosphere return to a strong El Niño-like pattern during the month of April. While El Niño is often associated with milder winters, El Niño is also notorious for chilly springs from the Great Lakes to the Maritimes. Back in February when we issued the forecast, we were already making the transition out of El Niño and we did not expect that major interruption in the transition that occurred during April.

In addition, unusually strong blocking developed in the upper atmosphere, first across the North Atlantic and then in the vicinity of Alaska. Blocking in the atmosphere in these regions often causes the jet stream to dip well to the south across central and eastern North America, and that is what we have often seen this spring.

What can the weather this spring tell us about the upcoming summer?

Unfortunately, one cannot make generalizations about the next season simply based on the current season. History shows us that for every cool spring that was followed by a cool summer, there was also a cool spring that was followed by a hot summer (and vice versa).


THE BIG REVEAL: Will a developing La Niña affect our summer as much as El Niño affected our winter? Tune in for the Summer Forecast on May 24 at 9pm EST and we'll help you plan your summer | SNEAK PEEK HERE


However, a cool spring does mean that the Great Lakes are still rather chilly, so lake shore areas have the potential to be considerably cooler when warmer weather reaches the region (read: why is it cooler by the lake). Also, in areas that are very dry at the end of spring, it can be more difficult to come out of that pattern as we get into the heart of summer. It certainly can be done if there is a major pattern change, but when the ground is very dry, the scattered late day showers and thunderstorms that we often see will be more sparse, and fronts that come through will have less moisture to work due to limited evapotranspiration (moisture being released into the atmosphere by vegetation etc.). The opposite is also true – regions that have a very wet spring can remain cooler and wetter into at least the early parts summer.

What is the process for developing a seasonal forecast?

There are two primary elements that we use to develop our seasonal forecasts. First, we analyze global weather patterns and sea surface temperature patterns and then we seek to identify years in the past that had similar patterns and study the weather patterns that were associated with those years across North America. Years in the past that had similar patterns to current and forecast patterns are called analogue years. Identifying the correct analogue years and researching their associated weather patterns is usually more helpful than the computer models when it comes to forecasting the weather patterns for upcoming seasons.

However, we do analyze computer models which are produced by weather services around the world. These models have some success in predicting how large scale patterns around the globe will evolve during the next few months. However, the models often disagree with each other or come up with forecasts that does not make sense meteorologically and we need to be able to recognize those errors.

What are the keys to the Summer 2016 Forecast?

The greatest challenge with this forecast is that we do not have any analogue years for this summer. In my above response I outlined how we depend heavily on using similar patterns in the past to provide insight on how future seasons will develop. However, for this summer we do not have any years that we can study that are strong matches to this summer.

There have been a few summers in which we were transitioning from a strong El Niño to a strong La Niña. However, the sea surface temperature patterns across the North Pacific and the North Atlantic were very different from what we have this year. There have been years that had a similar pattern in the North Pacific and North Atlantic to what we have now, but they were not associated with a transition to La Niña. To further add to the challenge, if we consider just years in which we transitioned into La Niña or just years with similar patterns in the oceans that surround North America, we get patterns that are opposite to each other. The models also seem to be wrestling with the contradictory signals from the ocean and atmosphere as there is a tremendous amount of disagreement between the models.

So, we have had to really piece together different parts of the puzzle to develop our forecast for the upcoming summer. To see the final result of this work, please check back on Tuesday, May 24 at 9:00 pm EDT when we release our forecast for the summer of 2016.

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