Southern Ontario chill: How cold is it?
Tuesday, February 17, 2015, 8:20 PM - Toronto is right on track to experience the coldest February in recorded history, while (potentially) never venturing above the freezing mark.
Ever hear of the saying, “Perception is key?” Well when it comes to weather, truer words could not exist.
While I cruelly ask you to re-live your memories of last winter, it’s important to remember this quote since it’s the few powerful events (or lack thereof) that help define our perception of a certain season. Last winter in southern Ontario, the events that come screaming back are most likely the ice storm and our ever-so-popular “polar vortex”, which kept us locked in an extended winter. After those scenarios, our perception was easy to form: one of the most intense and coldest winters ever.
So, would you believe me if I told you that this February is colder than last year’s?
As we released our winter outlook, we highlighted that we would see a slow start to winter before we saw the true, dominant pattern stabilize. This verified if we recall changing the lyrics of a classic to “I’m dreaming of a grey, dreary and unseasonably warm Christmas” (don’t worry, I won’t attempt to make another joke ever again).
When embarking on a seasonal outlook, our forecast team examines the general atmospheric patterns that will dominate our winter, specifically if there is a strong or weak El Nino setting up, among many other things. This year, we are on the weaker side, which is known for producing colder temperatures for eastern Canada, while a moderate to strong El Niño can signify a warmer winter across Canada. The difference from this year compared to last year’s forecast is the placement of the bulk of the arctic air – which shifted east from Manitoba to the Great Lakes.
As we ventured into February, our temperatures began to truly reflect this forecast. On average, our mean temperature is running about 3 degrees below last year’s (-8.3°C vs. -11.5°C) and 7 degrees below normal. Unfortunately, the remainder of the month looks to be playing by the same rules, as depicted in the next two images which show a model forecast for the final 10 days of February in five day increments.
These two figures Illustrate the forecast temperature departure from the normal temperature for the remainder of February. Oranges and browns show above seasonal departures (west coast), while blue, green and all the way to dark pink depict well-below seasonal temperatures (east coast).
Throughout recorded history at Pearson Airport, the coldest February award goes to the year of 1979 with a mean temperature of -10.8 degrees Celsius. While we are already cooler than the record, we still have the remainder of the month to go. If our current forecast holds true, we will claim this prestigious title, while staying below freezing, with the help from a few rounds of arctic air before reaching March.
Another interesting point to address is Lake Ontario. Throughout recorded (and reliable) history, the lake has only completely frozen over once back in 1934. To put in perspective, last year the most coverage we saw was around 62%, while the Great Lakes as a whole reported 92% coverage.
At this point in time, Lake Ontario is around 63% covered (see below).
Image from NASA's Terra Satellite on February 17th, 2015. On the right you can see that half of Lake Ontario still remains as open water. Bonus, completely unrelated, feature: a mesovortex over western Lake Ontario is spotted if you zoom in.
While extreme cold is without a doubt the most important ingredient when freezing a lake, calm conditions, particularly overnight, are what typically seal the deal. The logic behind this is if you have strong winds that produce more turbulent water surfaces, the cold water will be mixed by the upwelling of warmer water from below and will hinder the formation of ice, as well as break up newly-formed ice.
Could Lake Ontario triumphantly freeze over?
The conditions are certainly ripe as we head into the remainder of the month and into March. However, a lot of uncertainty remains and the lake requires a certain “Goldie-locks” set-up. As I mentioned, winds can ruin your potential for ice creation and with an active storm track just south of the Canadian and U.S. border, we will be fighting to see longer periods of calm winds.
Perception is key
Whether it be the milder start to winter, a balmy holiday season, potentially record-breaking cold or a frozen Lake Ontario, this winter will either go down in history as one of the worst or simply blend into the rest, depending on your perception.