Major Canadian cities on track for historic April cold
Meteorologist
Wednesday, April 25, 2018, 7:19 AM - Canadians either graciously accept winter with open arms or drag their feet the entire way. So for those who would willingly trade in the snow for sand, it's been a rough season that has been painfully etched into our memories after the ice storm.
But for some communities, April won't just be memorable... it will go down in history. How? Well there are so many fascinating statistics to swoon over that we need to nerd out together.
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While doing some number crunching for Toronto at Pearson International Airport, it wasn't an eye opener that April has been about 5°C below seasonal! Note: While we are using statistics for Pearson (since it's one of the most reliable climate data sets in Ontario), many of these stats generally apply across southern Ontario.
Image above: April statistics and climate normals from Toronto Lester B. Pearson International Airport. Data analysis from Matthew Grinter and Michael Carter.
Another stat that won't come as a surprise is the lack of warmth -- we have yet to crack 20ºC this April! Is that abnormal? Well in the 21st century it is. We've had over a dozen cases over the past 80 years where we have not reached 20 degrees in April. While we haven't finished the month yet, it seems unlikely with current forecast temperatures that we will top over 20ºC -- a monthly feat we haven't accomplished since 1999 (we will have to see if we can break the 20°C curse on April 30th).
Image above: Previous Aprils where temperatures did not reach or exceed 20ºC at Pearson International Airport. The months crossed off in orange indicate years where temperatures reached 20 in March, but not April. Data analysis from Matthew Grinter and Michael Carter.
So yes, that's quite impressive. However, when comparing average mean temperatures for April, the statistics get even more intriguing.
COLD APRIL
Taking the final forecast days of April into consideration, our average mean temperature (average between maximums and minimums) would equate to approximately 3°C for the month, meaning, drum roll... April 2018 will likely end up being in the top 5 of the coldest in recorded history.
Of course we will have to wait until the end of the month to officially declare it as some minor fluctuations in the forecast will occur.
Image above: Top Aprils with the coldest average mean temperatures for Toronto Lester B. Pearson International Airport. Climate data from 1938 through 2018. Data analysis from Matthew Grinter.
We also ran the numbers for Ottawa and April will also likely end up in the top 5 for the coldest average maximum temperatures in April. As The Weather Network's Chris Murphy said "It's like winning first place at the worst dressed competition."
COLD APRIL, BUT YOU CLAIM GLOBAL WARMING?
A common misunderstanding with global warming is that it should mean every single location heats up equally and we should never experience cold if our world is warming. As you can imagine, our atmosphere and the intertwined processes are complex. It isn't a simple cause and effect relationship and it's easy to treat weather and climate as the same entity. To understand the important difference, watch the video below.
CLIMATE VS. WEATHER -- THE IMPORTANT DIFFERENCE WITH CHIEF METEOROLOGIST CHRIS SCOTT
WHY THE SLOW START TO SPRING?
The slow start to spring can't be pinned on one cause, but is attributed to global patterns such as El Nino/La Nina, sea surface temperatures and sea ice (among many others). Scientists at Atmospheric and Environmental Research (AER) have been examining the link between sea ice extent in the Beaufort Sea and the colder temperatures in eastern North America, not just for this spring, but for the past few years.
Surface temperature anomalies (using a 1981-2010 climatology) for the Northern Hemisphere composited for April and May 2014, 2015, 2016 and 2017. Image Courtesy: Dr. Judah Cohen of AER. Blues depict colder than seasonal temperatures, oranges and reds depict warmer than seasonal temperatures.
Climatologist Dr. Judah Cohen from AER stated "The area that experienced the greatest warming the past four springs has been the North Pacific side of the Arctic. Warming in this region is related to ridging across Northwestern North America and into the Beaufort sea that would favor downstream troughing and relatively cool temperatures in Eastern Canada. That coupled with the unusually late retreat of eastern North America snow cover has contributed to a relatively cool spring across eastern North America and in some regions has been record cold."
WHAT'S AHEAD
Persistent warmth will be a struggle into May, even after a couple days of warm weather to start the month. "A period of cooler than normal temperatures is expected for May 4th to 10th and for mid and late May the signals are mixed," says The Weather Network's meteorologist Dr. Doug Gillham.
For a detailed analysis on what's ahead, make sure to read Your Weather First.
