We botched winter in areas, here are some reasons why
Visit the Complete Guide to Spring 2017 for the Spring Forecast, tips to survive it and much more.
Monday, February 27, 2017, 10:44 AM - Our winter forecast highlighted that this winter would bring a return to classic Canadian winter weather and that this winter would be quite different from the previous winter.
For most of Canada (geographically), this worked out very well. However, for a small percentage of the land (in which several million people live), this was truly a blown forecast. For the Greater Toronto Area, Niagara, and adjacent areas of southern and eastern Ontario, winter got off to a strong start in December, but January and February have been very mild with limited snowfall – not a classic Canadian winter!
So what happened? What follows is a discussion of the science behind the blown forecast and a look ahead to spring (Revealed today at 9 p.m. local. Full analysis and temperature maps availble online).
The Good, the Bad and the Ugly
First, I should highlight that the goal of any seasonal forecast is to capture the dominant jet stream pattern and communicate the weather that should result from that pattern. Even the best seasonal forecasts will never be perfect. The placement of lines between for above/below normal vs. normal temperature and precipitation is somewhat arbitrary but seeks to communicate the key weather story.
This winter, though, a couple of unexpected things happened.
First, we started to transition into an El Niño pattern. During the fall we did not see any indications that this would occur so quickly, but as the winter progressed, warmer than normal ocean water temperatures returned to the tropical Pacific, west of South America (see circled region on map below) and this contributed to the inability of winter weather to lock in across the eastern United States and adjacent areas of Canada.
The above map shows current sea surface temperature anomalies (how temperatures compare to "normal").
Second, the ring of warmer than normal ocean water temperatures in the northern Pacific Ocean to the west of Canada steadily eroded, with cooler than normal ocean water temperatures reaching nearly to the Canadian coastline (region circled in image below). This contributed to a jet stream pattern that allowed the Arctic air to be persistent across western Canada rather than spreading further east into the Great Lakes.
Finally, milder than normal temperatures in the Arctic (especially on our side of the pole) meant that when a jet stream pattern developed that was conducive to frigid weather in the Great Lakes, there was little truly Arctic air available to flood south into this region.
During the final week of January and the first 17 days of February, the jet stream pattern actually closely resembled what we had during February 2015 – one of the coldest Februaries on record, but the weather at the surface bore no resemblance to what we saw that year.
As we develop forecasts for an upcoming season, an important part of the process is looking back at years in the past that had similar global patterns, especially with regard to ocean water temperatures in the tropical Pacific.
Having a developing El Niño would typically be helpful as this is a stronger driver of seasonal weather patterns that has happened numerous times in the past. However, to have El Niño develop so soon after one of the strongest El Niño events on record is not something that has happened since we developed the ability to track such events.
With just being a year removed such a strong El Niño event, there is still a substantial amount of extra heat leftover in the atmosphere. Typically, when we have headed into El Niño we were also coming out a stronger La Niña of longer duration. However, the recent La Niña was weak and rather short-lived and that has left us with a unique global ocean water temperature pattern heading into our next El Niño. In some regards we are still heading out of and also heading into El Niño at the same time. This gives some contradictory signals in the long range global patterns.
GET READY FOR THE UNVEIL: What does all of this mean for our Spring 2017 forecast? Please check back on Monday, February 27 at 9 p.m. EST when we release our forecast for the months of March, April and May and a sneak peek at the upcoming summer season.