Does Edmonton Get Chinooks? Part 2

We're still in the middle of a coldsnap, but today it's time for Part 2 of "Does Edmonton Get Chinooks?"

In Part 1 we looked at the number of warm days and warm temperature swings that Edmonton sees from December through January. The simplest take-away from that was that during the deepest, darkest depths of winter our daytime highs break above 2°C about 25% of the time, and above 5°C about 11% of the time.

So it turns out that Edmonton winters aren't all -30°C all the time, and that we do actually get some mild temperatures. But do we get chinooks?

I think the best way to really answer this is to compare Edmonton to somewhere that does get chinooks. Luckily there's a city to the south of us that must get chinooks, because they're always naming stuff after them. And if Calgary is going to be our chinook-city, then we also a city without chinooks to act as a control, and Winnipeg should fill that role nicely. So today is basically going to be versus: Calgary & Winnipeg - Chinook Edition.

In Part 1 we looked at a few different approaches for quantifying how to spot a chinook:

• Warm Days
• daytime high of at least 2°C
• daytime high of at least 5°C
• daytime high of at least 10°C

• Warm Days with Temperature Swings
• daytime high of at least 5°C, with a day-over-day increase of at least 5°C
• daytime high of at least 8°C, with a day-over-day increase of at least 5°C
• daytime high of at least 2°C, with a day-over-day increase of at least 7°C

I don't know that any one of those is actually the "correct" definition, but by looking at all of them we get a nice range - we see how many times the temperature jumps up, as well as the overall number of warm days. So today we'll run through all of them again, but this time adding Calgary and Winnipeg for comparison. And we'll be sticking with the same December-February timeframe that we used last time.

All of the charts today will follow a standard format, with lines for the 5-year averages for Calgary, Edmonton and Winnipeg. I'm using 5-year averages today because otherwise things get very messy, but I have included Edmonton's yearly data in the background as a reference.

Days Above 2°C

Here we have the average number of days above 2°C for Calgary, Edmonton and Winnipeg, going back to the 1880s.

There are about 90 days in December, January and February, and in Part 1 we saw that Edmonton is above 2°C about 25% of the time, averaging around 22 days. Calgary is about double that at a little over 40 days, and Winnipeg (outside of a nice blip around 2000) is down around 3 or 4 days.

It's interesting how closely Edmonton and Calgary follow one another, with a lot of the same little peaks and dips showing up for both cities. It's also interesting that Calgary's line seems to be trending upwards since about the 1950s, while Edmonton's is more level. I'm not going to get into trends today though, because if I did that we would be here until spring.

Days Above 5°C

Here we have the average number of days above 5°C, and it looks pretty similar to the first chart, but the numbers have dropped a bit.

Right now Edmonton averages around 10 days, Calgary is up around 28 (and apparently trending upwards again), and Winnipeg is down at 1-in-about-every-4-years.

Days Above 10°C

And finally for the warm days, here we have days above 10°C.

Winnipeg is down at 0, with a few little blips in the 1940s and 1960s.

Edmonton isn't much higher, averaging about 1 per year. And looking at the yearly data which is in the background we can see that there are some years with no days above 10°C, and then others with 1 or 2 or 3. And as we saw last week, for some unexplained reason Edmonton's days above 10°C have really dropped off since the 1940s.

Calgary is well above the other two cities, averaging about 6 days above 10°C from December-February. But there's a pretty big range: from 1 in 2012-2013 to 19 in 2004-2005.

Temperature Swings

Warm temperatures are one thing, but are they necessarily chinooks? Last week we also looked at the temperature swings that go along with warm days, so lets go through those again:

High of at least 5°C with an increase of at least 5°C

Earlier today we looked at days above 5°C, and here we've narrowed that down to days above 5°C that were also at least 5°C warmer than the previous day. Here we're counting each chinook event instead of the total number of warm days, so the numbers have dropped compared to the earlier chart.

With this approach, Edmonton averages 2 or 3 of these chinook events per year. Recently that has ranged from 0 in 2008-2009 up to 6 in 2011-2012 and 7 in 2015-2016.

Calgary averages about 7 per year, with a range from 3 in 2009-2010 to 13 in 2011-2012.

Winnipeg gets one of these about every 5 years, although in 2011-2012 they had 2.

High of at least 8°C with an increase of at least 5°C

Very similar to what we were just looking at (but a little more challenging) here we have days above 8°C with an increase of at least 5°C. And here everyone's numbers have dropped.

Edmonton's average is down around 1 per year, and in recent history that's been split between some years with 0 and some with 2.

Calgary's average is about 4 per year, with a range of from 1 to 9.

And in Winnipeg these are very rare, only happening about once every 20 years.

High of at least 2°C with an increase of at least 7°C

Finally, we'll ease thing up a bit and drop the high temperature to at least 2°C, but this time we're looking for an increase of at least 7°C.

Here Edmonton averages about 4 events per year, with a range of 2 to 7. You have to go back to 1992-1993 to find a year without one.

Calgary's average is up at around 7 per year, ranging from 2 to 11.

And Winnipeg is back on the board at 1 per year, although that's skewed by having 4 in 2015-2016. More typically they get about one every-other-year.

Large Temperature Swings

In Part 1 I'd said that a temperature swing from 0°C to 5°C might not sound very impressive, but that those are just the minimum cutoffs. Within these results there are some genuinely large swings of 10°C, 20°C, or even 30°C. And this chart shows how these events breakdown for the three cities, from 1880 to 2016.

Not surprisingly, Calgary has the most, and has had day-over-day high temperature swings all the way up to 33°C.

Edmonton doesn't go quite that far, but we've got a nice chunk of days in the 5°C to 20°C range, and then a few more in the 20s.

Winnipeg has also had a handful of 20°C swings, but for the most part 12°C is their cutoff.

Over the 135 winters that are counted here, there were 41 of these events for Winnipeg, 435 for Edmonton, and 893 for Calgary.

Scorecard

At the end of the day, here is how everything adds up over the last 10 years.

In Part 1 we saw that Edmonton pretty reliably gets winter days above 2°C and 5°C, and that there are some decent temperature swings in there too. Today we have something that we can actually compare that to.

The reason that I included Winnipeg here wasn't because I was trying to be mean, but because I wanted a second frame of reference. If we were asking "Does Winnipeg Get Chinooks?" based on the numbers here I think the answer is a pretty easy "No." Winnipeg does occasionally get some mild winter temperatures, but they're not very common - compared to Calgary it's only about 5% or 10% as often.

For Edmonton it's a little bit trickier though, because the numbers aren't a total blow-out. Edmonton gets about a third or a half of what Calgary does, and even in the cases where Edmonton's numbers are low (days above 10°C, or 8°C with a 5°C increase) they're still reliable enough that they'll happen about every year.

So today isn't about saying that Edmonton gets chinooks that are as frequent or as big as Calgary -  if that was the case then people would have probably noticed it by now. Today is about comparing Edmonton to zero - as in "it never gets this warm in January" which is a popular sentiment in every, single January.

Calgary and southern Alberta celebrate their chinooks, and now we know that Edmonton gets about half of what Calgary does. So maybe Edmonton should try to look at the chinook-glass as half-full, instead of completely empty?

I'm pretty happy taking this glass-half-full approach, but in Part 3 we'll take one final look at chinooks, and see what happens to temperatures in Edmonton when Calgary has a chinook.