Lows of -25°C or Below
Highs of -15°C or Below
2016/12/31
This is a test
I just need a space to post a few fullsize images, and this is easiest.
Lows of -25°C or Below
Highs of -15°C or Below
Lows of -25°C or Below
Highs of -15°C or Below
January Preview
It's still December, but today we're going to take a look at the type of weather that January might have in store for us.
Normally I do these monthly previews at the same time that I do the reviews for the previous month, but this one is a little early because there will be plenty of year-end stuff to talk about in the next few days.
High Temperatures
Here we have Edmonton's January high temperatures for the last 20 years. With these tables the colours are really the most important part.
Anything in orange is a high above 0°C, and considering that here we're talking about January in Edmonton, that's a fair bit of orange. In the last 20 years the average number of days that broke the freezing mark was 11, which ranged from a low of 4 days to a high of 25. And in the last 10 years the average number of days above 5°C was 5, with 2008 as the only recent year that didn't have any.
And of course we can also see some blues and dark-blues for the cold days. In January we average about 5 days with highs below -15°C, and about 2 days with highs below -20°C.
Looking at the temperature distributions, Edmonton's average high temperature actually bottoms out around Christmas, and during January it's starting to climb back up. The same thing is true for the 25th and 75th percentiles.
That January warming is pretty slow though, and things don't start to really pick up until the start of February. And even though the average high and the quartiles have already turned around, the coldest-of-the-cold days that have been recorded were in late January.
Low Temperatures
Looking at the low temperatures, we don't see very many oranges for lows above freezing - 2013, 2014 and 2015 all had a few of them, but otherwise they've been pretty rare.
Typically most nights are below -10°C, and we average about 8 nights below -20°C and 4 below -25°C.
By January the high temperatures have already started to turn around, and we see something similar for the lows. They're not exactly rocketing back up yet, but they basically flatline from Christmas through about the third week of January. Although again, the coldest-of-the-cold days that have been recorded recently have been at the end of January.
Normally I do these monthly previews at the same time that I do the reviews for the previous month, but this one is a little early because there will be plenty of year-end stuff to talk about in the next few days.
High Temperatures
Here we have Edmonton's January high temperatures for the last 20 years. With these tables the colours are really the most important part.
Anything in orange is a high above 0°C, and considering that here we're talking about January in Edmonton, that's a fair bit of orange. In the last 20 years the average number of days that broke the freezing mark was 11, which ranged from a low of 4 days to a high of 25. And in the last 10 years the average number of days above 5°C was 5, with 2008 as the only recent year that didn't have any.
And of course we can also see some blues and dark-blues for the cold days. In January we average about 5 days with highs below -15°C, and about 2 days with highs below -20°C.
Looking at the temperature distributions, Edmonton's average high temperature actually bottoms out around Christmas, and during January it's starting to climb back up. The same thing is true for the 25th and 75th percentiles.
That January warming is pretty slow though, and things don't start to really pick up until the start of February. And even though the average high and the quartiles have already turned around, the coldest-of-the-cold days that have been recorded were in late January.
Low Temperatures
Looking at the low temperatures, we don't see very many oranges for lows above freezing - 2013, 2014 and 2015 all had a few of them, but otherwise they've been pretty rare.
Typically most nights are below -10°C, and we average about 8 nights below -20°C and 4 below -25°C.
2016/12/30
New Year's Eve
New Year's Day is technically the holiday, but I figure that New Year's Eve is the day that people spend more time outside, so it's the one that we'll be looking at.
Temperatures
In the last 30 years, the average high on New Year's Eve has been -8°C, with an average low of -16°C. Thinking back just one week, on Christmas Day the average is quite a bit warmer, with a high of -3°C and an low of -12°C
That being said, for some reason I tend to think of New Year's as not being super-cold, even though in recent years 2008, 2009, 2010 and 2013 have all dropped below -20°C. But the last few years have been pretty warm, with 2014 and 2015 both around 3°C.
And as with Christmas, the coldest New Year's Eve was also way back in the 1880s, at -42.8°C in 1884.
Precipitation
When we looked at Christmas Day, it had been mostly precipitation-free recently. But for New Year's eve the chances of getting snow have been about 50/50. There hasn't been a major, 10cm snow on New Year's since 1967 though.
Snow of the Ground
The amount of snow on the ground is similar (not surprisingly) to what we saw with Christmas Day: from 1997 through 2005 it was pretty low fluctuating between 0cm and 10cm, but more recently we've fluctuated between about 5cm and 30cm.
Temperatures
In the last 30 years, the average high on New Year's Eve has been -8°C, with an average low of -16°C. Thinking back just one week, on Christmas Day the average is quite a bit warmer, with a high of -3°C and an low of -12°C
That being said, for some reason I tend to think of New Year's as not being super-cold, even though in recent years 2008, 2009, 2010 and 2013 have all dropped below -20°C. But the last few years have been pretty warm, with 2014 and 2015 both around 3°C.
And as with Christmas, the coldest New Year's Eve was also way back in the 1880s, at -42.8°C in 1884.
Precipitation
When we looked at Christmas Day, it had been mostly precipitation-free recently. But for New Year's eve the chances of getting snow have been about 50/50. There hasn't been a major, 10cm snow on New Year's since 1967 though.
Snow of the Ground
The amount of snow on the ground is similar (not surprisingly) to what we saw with Christmas Day: from 1997 through 2005 it was pretty low fluctuating between 0cm and 10cm, but more recently we've fluctuated between about 5cm and 30cm.
2016/12/23
Christmas
This is a few days early, but here's a look at Edmonton's Christmas Day weather history.
Temperatures
In the last 30 years, the average high on Christmas day has been a pretty balmy -3°C, with an average low of -12°C. That bounces around a bit though, with 2008, 2012 and 2015 all being reasonably chilly and down around -20°C, while 2011 and 2013 were up above freezing.
The coldest-ever recorded Christmas was also the first recorded Christmas, with a low of -39.4°C back in 1880.
Precipitation
In terms of precipitation, Christmas day has been pretty free of snow and rain, with 2004 and 2014 being the only recent Christmases to record any snow.
Snow of the Ground
And I've mentioned before that I'm never sure exactly how much to trust Environment Canada's snow-on-ground measurement?
But from 1997 through 2005 Christmas snow was apparently pretty minimal, fluctuating between 0cm and 10cm for about a decade. More recently we've been fluctuating between about 5cm and 25cm.
As I write this on December 23, 2016, Environment Canada is showing 5cm on the ground at the International, and 2cm at Blatchford. Around downtown we're actually getting pretty close to "trace" amounts, with plenty of grass showing up in the sunny spots.
Temperatures
In the last 30 years, the average high on Christmas day has been a pretty balmy -3°C, with an average low of -12°C. That bounces around a bit though, with 2008, 2012 and 2015 all being reasonably chilly and down around -20°C, while 2011 and 2013 were up above freezing.
The coldest-ever recorded Christmas was also the first recorded Christmas, with a low of -39.4°C back in 1880.
Precipitation
In terms of precipitation, Christmas day has been pretty free of snow and rain, with 2004 and 2014 being the only recent Christmases to record any snow.
Snow of the Ground
And I've mentioned before that I'm never sure exactly how much to trust Environment Canada's snow-on-ground measurement?
But from 1997 through 2005 Christmas snow was apparently pretty minimal, fluctuating between 0cm and 10cm for about a decade. More recently we've been fluctuating between about 5cm and 25cm.
As I write this on December 23, 2016, Environment Canada is showing 5cm on the ground at the International, and 2cm at Blatchford. Around downtown we're actually getting pretty close to "trace" amounts, with plenty of grass showing up in the sunny spots.
2016/12/19
Does Edmonton Get Chinooks? Part 3 - Chinook Echoes
We've left the recent coldsnap behind - on the weekend the temperature swung from a low of -27°C on Saturday to a high of 3°C on Sunday, and now there are wind warnings everywhere - so this seems like the perfect time to take one final look at the question of chinooks in Edmonton.
In Part 1 we saw that Edmonton reliably gets some mild temperatures in the middle of winter. And in Part 2 we saw that whether you actually want to call them "chinooks" or not, Edmonton gets about half of what Calgary does, and a lot more than Winnipeg.
Today we're going to take a different approach, and see what happens to the temperatures in Edmonton when Calgary gets a chinook.
Calgary Winter Temperatures
Here are Calgary's daily high temperatures for December-February for the last 5 years. Highs above freezing are in orange, and below freezing are in blue. In our other looks at chinooks I had been using data that went all the way back to the 1880s, but today we're going to stick with recent history because otherwise things get very complicated.
Now lets take a look at the chinooks:
Calgary Chinooks
Here the daily temperatures are still in the background, and the red lines show each time that Calgary had a chinook. We've looked at a few different ways to quantity a chinook, and today I'm just going to focus on one of them:
Just for a little bit of context, this week both Calgary and Edmonton are emerging from an early-December deepfreeze, but right now neither city has any temperatures above 5°C in the forecast. So even though both cities will have swung from below -20°C to above freezing, it won't actually count as a chinook unless we warm up a little bit more than expected.
For these past 5 winters then, Calgary had 31 of these chinook events. And we can see that some of them had temperature swings right around the 5°C minimum, whereas others were almost 20°C. 2011-2012 and 2013-2014 each had 8 of these events, while 2012-2013 only 3 events, although the number of events doesn't necessarily relate to how long each event lasted, or how warm things actually got.
Now lets take a look at what happened in Edmonton while Calgary was warming up:
Edmonton Temperatures During Chinooks
This isn't a great chart, but it's one step on the way to a better one, so we won't spend too here before moving on.
Here we've added the temperatures for Edmonton each time that Calgary has a chinook. The lines in orange are days when Edmonton warmed up, and blue are days when Edmonton got colder. Of the 31 Calgary chinooks, Edmonton cooled off only 4 times, and warmed up the other 27.
To make things easier to read we're going to get rid of all the non-chinook days, and just focus on the days that Calgary's temperature jumps up:
Temperature Changes
Here is the same data as the last chart, but now we're just looking at the temperatures at the start of the Calgary chinooks. I think this makes it a little easier to see what's going on.
The 4 days that Edmonton cooled off are still in blue, and the days with warming are in orange. Of those warm days in orange, we can see that Edmonton had some pretty substantial temperature increases, as well as some tiny little ones.
One thing that we didn't talk about last week, is that Edmonton is quite a bit further from the mountains than Calgary is. So maybe it takes longer for the warm air to get here? Instead of just looking at the one-day temperature increase, today I'd like to add a second day into the mix as well, to see what happens over 48 hours.
Temperature Changes over 48 Hours
Here is same data that we were just looking at, but now the second day of each chinook has been added as a lighter line. In some cases Day 2 is actually colder than Day 1, and those aren't shown - this is the maximum high temperature swing for both cities over 48 hours.
One thing to notice is that now there's only one blue line, because for these 31 Calgary chinooks Edmonton's temperature only dropped once over 48 hours. If we look at the last chinook in the chart as example - February 4th, 2015-2016 - we can see that on Day 1 Edmonton's temperature fell from -1°C to -4°C, but then on Day 2 it jumped up by 10°C to reach 6°C. That sort of thing is why I was interested in looking at a 48-hour window, instead of just 24.
So here we can see a number of large temperature swings for Calgary and Edmonton, but it's a little tough to compare everything because all of the starting and ending temperatures are different.
48-Hour Temperature Increase
Here the temperature swings from the previous chart have all be given them all the same starting point of 0. So now instead of looking at where the temperature started and ended on those days, this just show us how much the temperature increased.
Lining things up like this makes it easier to see how Calgary's chinooks compare to one another, and how Edmonton's temperature change compared to Calgary's. The Calgary chinooks vary from a minimum temperature swing of 7°C, all the way up to three with swings of 21°C. Edmonton also had two days with swings above 20°C, but then there's also one around the 1°C mark, and the one day that got colder.
When we group these all together we end up with this:
For the 31 Calgary chinooks that we've been looking at from the last 5 winters, when Calgary's temperature jumped up Edmonton's usually did too.
About 80% of the time Edmonton warmed up by at least half as much as Calgary did. Of these 31 chinooks there were only 6 when Edmonton's increase was less than half of Calgary's, but that's balanced against the 5 where Edmonton's temperature increased more than Calgary's.
So even if we don't get a full chinook, it seems like a lot of the time we maybe get an echo.
And after all of that, we finally get to our last set of charts for today:
Chinook Echoes
The previous chart we looked at showed how much Edmonton's temperature changes relative to Calgary's. That's handy, because now we know that when Calgary warms up for a chinook we usually warm up too - so we should be cheering on our southern neighbours, because we get some of the benefit. But that chart didn't tell us where Edmonton's temperature actually ended up, so that's what we have here.
This chart shows the same 31 recent chinooks that we've been looking at. Up-and-down is Edmonton's highest temperature in the 48-hour period, and right-to-left is how Edmonton's temperature jump compared to Calgary's.
Anything in the upper-right part of the chart is pretty good, because it means that our temperature jumped up as-much-or-more than Calgary's did, and the temperature also reached above 5°C. We also see some days where our temperature jump was similar to Calgary's, but where we only reached 0°C or 2°C. And then there are the days when there's not much going on, because we're stuck down around -5°C or -10°C.
Now lets look at the same chart, but this time including all of recorded history:
Here we have what happened to Edmonton temperatures when Calgary had a chinook, for all the chinooks going back to 1880.
In the chart I've broken things into four (somewhat arbitrary) groups:
But today what we've seen is that when Calgary does get chinook-like temperatures:
Calgary and southern Alberta celebrate their chinooks, and I think we've seen that Edmonton could do a bit of that too, if we were so inclined. Personally, I'm already looking forward to the chinooks and chinook-echoes that we'll see over the next few months.
This brings us to the end of Edmonton Weather Nerdery's epic look at whether-or-not Edmonton gets chinooks.
In Part 1 we saw that Edmonton reliably gets some mild temperatures in the middle of winter. And in Part 2 we saw that whether you actually want to call them "chinooks" or not, Edmonton gets about half of what Calgary does, and a lot more than Winnipeg.
Today we're going to take a different approach, and see what happens to the temperatures in Edmonton when Calgary gets a chinook.
Calgary Winter Temperatures
Here are Calgary's daily high temperatures for December-February for the last 5 years. Highs above freezing are in orange, and below freezing are in blue. In our other looks at chinooks I had been using data that went all the way back to the 1880s, but today we're going to stick with recent history because otherwise things get very complicated.
Now lets take a look at the chinooks:
Calgary Chinooks
Here the daily temperatures are still in the background, and the red lines show each time that Calgary had a chinook. We've looked at a few different ways to quantity a chinook, and today I'm just going to focus on one of them:
- days with a high of at least 5°C and a day-over-day increase of at least 5°C.
Just for a little bit of context, this week both Calgary and Edmonton are emerging from an early-December deepfreeze, but right now neither city has any temperatures above 5°C in the forecast. So even though both cities will have swung from below -20°C to above freezing, it won't actually count as a chinook unless we warm up a little bit more than expected.
For these past 5 winters then, Calgary had 31 of these chinook events. And we can see that some of them had temperature swings right around the 5°C minimum, whereas others were almost 20°C. 2011-2012 and 2013-2014 each had 8 of these events, while 2012-2013 only 3 events, although the number of events doesn't necessarily relate to how long each event lasted, or how warm things actually got.
Now lets take a look at what happened in Edmonton while Calgary was warming up:
Edmonton Temperatures During Chinooks
This isn't a great chart, but it's one step on the way to a better one, so we won't spend too here before moving on.
Here we've added the temperatures for Edmonton each time that Calgary has a chinook. The lines in orange are days when Edmonton warmed up, and blue are days when Edmonton got colder. Of the 31 Calgary chinooks, Edmonton cooled off only 4 times, and warmed up the other 27.
To make things easier to read we're going to get rid of all the non-chinook days, and just focus on the days that Calgary's temperature jumps up:
Temperature Changes
Here is the same data as the last chart, but now we're just looking at the temperatures at the start of the Calgary chinooks. I think this makes it a little easier to see what's going on.
The 4 days that Edmonton cooled off are still in blue, and the days with warming are in orange. Of those warm days in orange, we can see that Edmonton had some pretty substantial temperature increases, as well as some tiny little ones.
One thing that we didn't talk about last week, is that Edmonton is quite a bit further from the mountains than Calgary is. So maybe it takes longer for the warm air to get here? Instead of just looking at the one-day temperature increase, today I'd like to add a second day into the mix as well, to see what happens over 48 hours.
Temperature Changes over 48 Hours
Here is same data that we were just looking at, but now the second day of each chinook has been added as a lighter line. In some cases Day 2 is actually colder than Day 1, and those aren't shown - this is the maximum high temperature swing for both cities over 48 hours.
One thing to notice is that now there's only one blue line, because for these 31 Calgary chinooks Edmonton's temperature only dropped once over 48 hours. If we look at the last chinook in the chart as example - February 4th, 2015-2016 - we can see that on Day 1 Edmonton's temperature fell from -1°C to -4°C, but then on Day 2 it jumped up by 10°C to reach 6°C. That sort of thing is why I was interested in looking at a 48-hour window, instead of just 24.
So here we can see a number of large temperature swings for Calgary and Edmonton, but it's a little tough to compare everything because all of the starting and ending temperatures are different.
48-Hour Temperature Increase
Here the temperature swings from the previous chart have all be given them all the same starting point of 0. So now instead of looking at where the temperature started and ended on those days, this just show us how much the temperature increased.
Lining things up like this makes it easier to see how Calgary's chinooks compare to one another, and how Edmonton's temperature change compared to Calgary's. The Calgary chinooks vary from a minimum temperature swing of 7°C, all the way up to three with swings of 21°C. Edmonton also had two days with swings above 20°C, but then there's also one around the 1°C mark, and the one day that got colder.
When we group these all together we end up with this:
For the 31 Calgary chinooks that we've been looking at from the last 5 winters, when Calgary's temperature jumped up Edmonton's usually did too.
About 80% of the time Edmonton warmed up by at least half as much as Calgary did. Of these 31 chinooks there were only 6 when Edmonton's increase was less than half of Calgary's, but that's balanced against the 5 where Edmonton's temperature increased more than Calgary's.
So even if we don't get a full chinook, it seems like a lot of the time we maybe get an echo.
And after all of that, we finally get to our last set of charts for today:
Chinook Echoes
The previous chart we looked at showed how much Edmonton's temperature changes relative to Calgary's. That's handy, because now we know that when Calgary warms up for a chinook we usually warm up too - so we should be cheering on our southern neighbours, because we get some of the benefit. But that chart didn't tell us where Edmonton's temperature actually ended up, so that's what we have here.
This chart shows the same 31 recent chinooks that we've been looking at. Up-and-down is Edmonton's highest temperature in the 48-hour period, and right-to-left is how Edmonton's temperature jump compared to Calgary's.
Anything in the upper-right part of the chart is pretty good, because it means that our temperature jumped up as-much-or-more than Calgary's did, and the temperature also reached above 5°C. We also see some days where our temperature jump was similar to Calgary's, but where we only reached 0°C or 2°C. And then there are the days when there's not much going on, because we're stuck down around -5°C or -10°C.
Now lets look at the same chart, but this time including all of recorded history:
Here we have what happened to Edmonton temperatures when Calgary had a chinook, for all the chinooks going back to 1880.
In the chart I've broken things into four (somewhat arbitrary) groups:
- What I am going to call "chinooks", where Edmonton warmed up by at least 75% as much as Calgary did, and our temperature broke 5°C
- Chinook echoes, where we either warmed up by at least half as much as Calgary did, or we only ended up between 0°C and 5°C.
- Days where we didn't see much of a temperature change compared to Calgary, but it was still above freezing (and in many cases above 5°C).
- And then there are all the rest, where we didn't see much of a jump or it stayed pretty cool.
But today what we've seen is that when Calgary does get chinook-like temperatures:
- 30% of the time Edmonton sees something similar
- 33% of the time we get a weaker echo
- 11% of the time we're pretty warm anyway
- and for the remaining 27% we may or may not warm up, but we don't break freezing.
Calgary and southern Alberta celebrate their chinooks, and I think we've seen that Edmonton could do a bit of that too, if we were so inclined. Personally, I'm already looking forward to the chinooks and chinook-echoes that we'll see over the next few months.
This brings us to the end of Edmonton Weather Nerdery's epic look at whether-or-not Edmonton gets chinooks.
2016/12/17
Third Place
With our recent coldsnap coming to an end, 2016 has now fallen to 3rd place in the race for Warmest-Recorded-Year, as of December 16:
Just 2 weeks left to see where it ends up.
(if you're curious what this chart is actually supposed to mean, it's easiest to read the full explanation: How warm is 2016?)
Just 2 weeks left to see where it ends up.
(if you're curious what this chart is actually supposed to mean, it's easiest to read the full explanation: How warm is 2016?)
2016/12/12
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:
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.
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.
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
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.
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.
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
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
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.
2016/12/06
'Tis the season of -20°C
As -20°C looms, today we're going to look at when throughout the winter we are likely to get extreme temperatures.
Here is a recent history of when the temperature first dips below -20°C each winter:
First -20°C Each Winter
For the last few years, the first -20°C has shown up in mid-to-late November. 2010-2011 is roughly as long as I've been biking year-round, and I'm always wary of the end of November because it often brings a sudden blast of real-winter.
But that hasn't always been the case, and going back to 1995 we see a lot of years where -20°C didn't show up until December or even January. So this year is a little late in terms of recent history, but it's not unusual even going back 20 years.
For the rest of today we're going to look at the whole winter, and at how the likelihood of really cold days changes as we move from November through March. And because I don't want today to be entirely discouraging, we'll be looking at the extremely warm days as well as the extremely cold ones.
Likelihood of Warm & Cold Days
Here I've broken the winter down into weeks, and the orange and blue lines show the likelihood of experiencing at least one day with a High above 0°C or a Low below -20°C in each week. This is based on the temperatures for Blatchford for the last 20 years.
I've underlined "at least one day" up above because it's an important part of this. This isn't trying to count all of the cold days, or looking at how long a coldsnap or warmspell typically lasts. This is just trying to give a timeline of when we might expect warm or cold weather, even if only briefly.
Using the first week of January as an example: for Highs above 0°C the number is 75%, and for Lows below -20°C it is 60%. That doesn't mean that the week will be 75% above 0°C and 60% below -20°C. It just means that in the last 20 years, during the first week of January, in 15-of-20 years there was at least one day above 0°C, and in 12-of-20 years there was at least one night below -20°C.
So why did I do this chart? The goal is really to psych myself up for the winter. Days below -20°C mean wearing a whole bunch of extra gear (including putting boots on the dog when she goes for a walk), and this gives me an idea of how long that season might last.
-20°C can arrive as early as the second week of November, and it might not leave until April. But it's only in late-December and early-January that there's more than a 50/50 chance of dipping down below -20°C. So with this I can see that I need to keep the mitts and longjohns and dogboots handy for 5 months, but they'll get most of their use in December, January, and then the cruel joke that is early-March.
The flipside is the days above 0°C. Here we can see that for any given week of the winter we are always more likely to see a warm day than a cold one. Even in January there's a 70% chance that any week will pop up above the freezing mark. The one oddball is the first week of December, which is only at the 55% mark for some reason.
I've said before that I like using 0°C and -20°C as ranges, because they're representative of a pretty nice winter day, or a pretty chilly one. But now lets look at some of the real extremes.
Cold Days
Here's the same data, but this time looking at only the cold days: the Lows below -20°C, -25°C and -30°C. The really cold days follow -20°C pretty closely, with the peak in January, and that same annoying hump in early March.
For lows below -30°C the range is between 0 and 20% depending on the week. So even for the worst weeks - the 2nd and 4th of January - only 4 of the last 20 years have had any days that cold. Although the 2nd week of January has dropped below -25°C in 10 out of the last 20 years.
We shouldn't be too depressed though, because the chances of extremely cold days are much lower than the used to be:
This is an update of a chart that I used for one of my very first posts. It shows how the number of very cold days that Edmonton gets each winter has fallen over the years.
Nowadays the low drops below -20°C an average of only 23 times a year. Although that can range from only 6 times in a winter like 2015-2016, to 46 in 2010-2011.
Warm Days
Here we have the warm winter days. As we saw earlier, for most weeks of the winter there has been at least a 70% chance of a day above 0°C, with the only exception being the first week of December.
Even for days above 5°C, the lowest likelihood is 30%. So 6 out of the last 20 years have had at least one day above 5°C in the last week of December, or in the middle of January.
Winter days above 10°C are definitely pretty rare though, which we saw when we looked at chinooks. For most of November through February the likelihood is 20% or less. And in the last 20 years there have been no days above 10°C in the 3rd week of December, the 2nd-4th weeks of January, or the 1st week of February.
At the beginning of November this year we had a few weeks of very warm weather, which were pretty unusual. In the first week of November the chances of days above 10°C are only 40%, and for the second and third weeks it's about 20%.
Here we have the warm days and the cold days combined, which looks neat, even if it's is pretty hard to read.
Generally the warm days dwarf the cold ones. For most weeks of the winter - except for late-December and early-January - we're more likely to see a day above 5°C than a low below -20°C. And the highs above 10°C and lows below -30°C trade-off which each other, with the +10s disappearing at the same time that the -30s peak.
Everything today has been about the likelihood of any given week getting a warm or a cold day. Another way to look at this would be the number of days each week that are warm or cold, and so here is one final chart:
Average Days per Week
This is the average number of days each week that are above 0°C, or below -20°C.
Averages are a bit tricky, because they're not necessarily representative of any given year. So when we see an "average" of 2.4 Lows below -20°C in the first week of January, what that really means is that there are some cold years when most of the week is below -20°C, balanced against the warm years with no -20s. That's just something to keep in mind when looking at this chart, and it's why I started today with the at-least-one-day approach.
The general shape of these timelines is pretty similar to what we saw in the first chart today: winter peaks in early January; things ease off in February; and there is an early-March bounce to keep us on our toes. And here we see that in the darkest depths of winter at the beginning of January we get just about as many total days above 0°C as we do nights below -20°C.
Here is a recent history of when the temperature first dips below -20°C each winter:
First -20°C Each Winter
For the last few years, the first -20°C has shown up in mid-to-late November. 2010-2011 is roughly as long as I've been biking year-round, and I'm always wary of the end of November because it often brings a sudden blast of real-winter.
But that hasn't always been the case, and going back to 1995 we see a lot of years where -20°C didn't show up until December or even January. So this year is a little late in terms of recent history, but it's not unusual even going back 20 years.
For the rest of today we're going to look at the whole winter, and at how the likelihood of really cold days changes as we move from November through March. And because I don't want today to be entirely discouraging, we'll be looking at the extremely warm days as well as the extremely cold ones.
Likelihood of Warm & Cold Days
Here I've broken the winter down into weeks, and the orange and blue lines show the likelihood of experiencing at least one day with a High above 0°C or a Low below -20°C in each week. This is based on the temperatures for Blatchford for the last 20 years.
I've underlined "at least one day" up above because it's an important part of this. This isn't trying to count all of the cold days, or looking at how long a coldsnap or warmspell typically lasts. This is just trying to give a timeline of when we might expect warm or cold weather, even if only briefly.
Using the first week of January as an example: for Highs above 0°C the number is 75%, and for Lows below -20°C it is 60%. That doesn't mean that the week will be 75% above 0°C and 60% below -20°C. It just means that in the last 20 years, during the first week of January, in 15-of-20 years there was at least one day above 0°C, and in 12-of-20 years there was at least one night below -20°C.
So why did I do this chart? The goal is really to psych myself up for the winter. Days below -20°C mean wearing a whole bunch of extra gear (including putting boots on the dog when she goes for a walk), and this gives me an idea of how long that season might last.
-20°C can arrive as early as the second week of November, and it might not leave until April. But it's only in late-December and early-January that there's more than a 50/50 chance of dipping down below -20°C. So with this I can see that I need to keep the mitts and longjohns and dogboots handy for 5 months, but they'll get most of their use in December, January, and then the cruel joke that is early-March.
The flipside is the days above 0°C. Here we can see that for any given week of the winter we are always more likely to see a warm day than a cold one. Even in January there's a 70% chance that any week will pop up above the freezing mark. The one oddball is the first week of December, which is only at the 55% mark for some reason.
I've said before that I like using 0°C and -20°C as ranges, because they're representative of a pretty nice winter day, or a pretty chilly one. But now lets look at some of the real extremes.
Cold Days
Here's the same data, but this time looking at only the cold days: the Lows below -20°C, -25°C and -30°C. The really cold days follow -20°C pretty closely, with the peak in January, and that same annoying hump in early March.
For lows below -30°C the range is between 0 and 20% depending on the week. So even for the worst weeks - the 2nd and 4th of January - only 4 of the last 20 years have had any days that cold. Although the 2nd week of January has dropped below -25°C in 10 out of the last 20 years.
We shouldn't be too depressed though, because the chances of extremely cold days are much lower than the used to be:
This is an update of a chart that I used for one of my very first posts. It shows how the number of very cold days that Edmonton gets each winter has fallen over the years.
Nowadays the low drops below -20°C an average of only 23 times a year. Although that can range from only 6 times in a winter like 2015-2016, to 46 in 2010-2011.
Warm Days
Here we have the warm winter days. As we saw earlier, for most weeks of the winter there has been at least a 70% chance of a day above 0°C, with the only exception being the first week of December.
Even for days above 5°C, the lowest likelihood is 30%. So 6 out of the last 20 years have had at least one day above 5°C in the last week of December, or in the middle of January.
Winter days above 10°C are definitely pretty rare though, which we saw when we looked at chinooks. For most of November through February the likelihood is 20% or less. And in the last 20 years there have been no days above 10°C in the 3rd week of December, the 2nd-4th weeks of January, or the 1st week of February.
At the beginning of November this year we had a few weeks of very warm weather, which were pretty unusual. In the first week of November the chances of days above 10°C are only 40%, and for the second and third weeks it's about 20%.
Here we have the warm days and the cold days combined, which looks neat, even if it's is pretty hard to read.
Generally the warm days dwarf the cold ones. For most weeks of the winter - except for late-December and early-January - we're more likely to see a day above 5°C than a low below -20°C. And the highs above 10°C and lows below -30°C trade-off which each other, with the +10s disappearing at the same time that the -30s peak.
Everything today has been about the likelihood of any given week getting a warm or a cold day. Another way to look at this would be the number of days each week that are warm or cold, and so here is one final chart:
Average Days per Week
This is the average number of days each week that are above 0°C, or below -20°C.
Averages are a bit tricky, because they're not necessarily representative of any given year. So when we see an "average" of 2.4 Lows below -20°C in the first week of January, what that really means is that there are some cold years when most of the week is below -20°C, balanced against the warm years with no -20s. That's just something to keep in mind when looking at this chart, and it's why I started today with the at-least-one-day approach.
The general shape of these timelines is pretty similar to what we saw in the first chart today: winter peaks in early January; things ease off in February; and there is an early-March bounce to keep us on our toes. And here we see that in the darkest depths of winter at the beginning of January we get just about as many total days above 0°C as we do nights below -20°C.
2016/11/30
November Review / December Preview
Daytime Highs
After our little heatwave at the beginning of the month the High temperatures dropped down to right around the 20-year average.
With 9 days above 10°C this November had more than any year going back to 1997. But the average high of 5°C was a little bit lower than November of 2009, which was more consistently warm for the whole month and which didn't have a single High below 0.
Daytime Lows
After the heatwave the Low temperatures had a similar drop, but still stayed about 5°C above the average through the end of the month.
With 9 nights above 0°C, none below -10°C, and an average overnight low of -2°C this November had the warmest lows, going back to 1997.
This was also the first November since 2009 that didn't have any temperatures below -20°C. In the last 6 years those sudden blasts of real-winter have been a fixture of late November.
Precipitation
Overall precipitation for the month was right around the average. The Edmonton International is missing snowfall records for this month, but in the downtown area we didn't get more that a light dusting all month. Downtown did, however, get a few genuine November downpours.
December
For December, looking at the High temperatures about half of the time we can see a fair number of oranges, for temperatures above 0°C or even 5°C. And not surprisingly, we also see some blues for highs below -10°C or even -20°C. But really, there's a lot of orange in there, isn't there?
For the Low temperatures, December nights above 0°C are pretty rare: 2014, 2011, 2004, 2002, 1999 all had some. And lows below -20°C are almost a given, with the only years without them being 2011, 2002, and 1997.
Warmest-Recorded-Year
Finally, with one month left in the race, 2016 is still in the lead for warmest-recorded-year. The heatwave at the beginning of November was enough to undo the coldsnap of early October, and right now things are very tight.
To gets "points" during the next month December doesn't have to be hot - it just has to be above the 20th century average which is about -6°C for the High and -15°C for the Low. Days that are warmer than that will send the line up, and colder days will drop it down.
December of 1981 was warm, but then its final week really dropped off with several days around -30°C. And right now our forecast for next week is calling for some -20°C's. So we might have to wait until New Year's to know exactly where 2016 will end up.
With 9 days above 10°C this November had more than any year going back to 1997. But the average high of 5°C was a little bit lower than November of 2009, which was more consistently warm for the whole month and which didn't have a single High below 0.
Daytime Lows
After the heatwave the Low temperatures had a similar drop, but still stayed about 5°C above the average through the end of the month.
With 9 nights above 0°C, none below -10°C, and an average overnight low of -2°C this November had the warmest lows, going back to 1997.
This was also the first November since 2009 that didn't have any temperatures below -20°C. In the last 6 years those sudden blasts of real-winter have been a fixture of late November.
Precipitation
December
For December, looking at the High temperatures about half of the time we can see a fair number of oranges, for temperatures above 0°C or even 5°C. And not surprisingly, we also see some blues for highs below -10°C or even -20°C. But really, there's a lot of orange in there, isn't there?
For the Low temperatures, December nights above 0°C are pretty rare: 2014, 2011, 2004, 2002, 1999 all had some. And lows below -20°C are almost a given, with the only years without them being 2011, 2002, and 1997.
Warmest-Recorded-Year
Finally, with one month left in the race, 2016 is still in the lead for warmest-recorded-year. The heatwave at the beginning of November was enough to undo the coldsnap of early October, and right now things are very tight.
To gets "points" during the next month December doesn't have to be hot - it just has to be above the 20th century average which is about -6°C for the High and -15°C for the Low. Days that are warmer than that will send the line up, and colder days will drop it down.
December of 1981 was warm, but then its final week really dropped off with several days around -30°C. And right now our forecast for next week is calling for some -20°C's. So we might have to wait until New Year's to know exactly where 2016 will end up.
2016/11/28
Does Edmonton Get Chinooks? Part 1
I was all set to talk about blizzards today, but since there's no snow on the ground that doesn't really feel appropriate. So instead we're going to look at chinooks.
I think that most people in Alberta will be familiar with the term "chinook", but I never know how widely known it is elsewhere? I won't copy the entire wikipedia entry, but the name is a reference to the Chinook people from what is now Oregon and Washington, and a chinook is when air from the west coast spills over the Rockies bringing dry, windy and unseasonably warm winter weather.
The sourthern part of Alberta up through Calgary is famous for chinooks, with temperatures swinging from below freezing to above 15°C in a few hours. That leads to folklore like:
Just as a caveat, I'm not going to look at the actual mechanism of chinooks, or whether coastal air really does make it's way all the way to Edmonton. I'm just going to look at temperatures to see how often we get changes that could be maybe considered chinook-like.
Today is Part 1 and (spoilers) there won't be any answers. Those will have to wait until Part 2.
To get started, exactly how warm do temperatures have be to qualify as a chinook? Googling around, I can't find an easy answer, so we're going to look at a few approaches.
Warm Days
I found this 50-year-old study online which I'm going to use as a starting point: Richmond W. Longley (1967) The frequency of winter Chinooks in Alberta, Atmosphere, 5:4, 4-16
Longley hints at what I'm interested in - we might not get the same warm extremes as the southern part of the province, but we get something. Is it enough to be called a chinook? That paragraph mentions three different temperature ranges:
Here we have the number of days above 2°C, 5°C and 10°C for December-February going back to the 1880s.
For days above 2°C we get between about 15 and 30 days. There have been some low years like 1992-1993 which only had 1, but also years like 2011-2012 with 39, and last winter with 34.
For days above 5°C we get between about 5 and 15 days. And days above 10°C are fairly rare, with many years that don't have any during December-February.
To get a better sense of the trends, here is the same data with the 5-year averages added as dotted lines:
Looking at the averages, during December-February we get about 23 days above 2°C, and about 10 days above 5°C. Those three coldest months of the year have 89 days (90 in leap-years), and so we break 2°C about 25% of the time, and for 5°C it's about 11%.
One thing that stands out here is that the number of days above 10°C has dropped off in the last 100 years - the average used to be 2 or 3 days per year, but now it's down below 1. We actually saw this before, in one of my earliest posts.
Whenever I see strange numbers from a century ago I start to question the data. Edmonton has had a few weather stations over the years (which I talked about here). The first switch happened in 1937, and looking at this chart 1937 is about the point where the frequency of those 10°C days really drops. And when I'd compared the data from the stations, I'd found that the oldest 1880-1937 station was more variable than the newer ones. So it's possible that in the olden-days we really did get more warm days in December-February than we do today, or it's possible that the older data was a little less precise. For now, we'll leave it as a mystery.
If days above 10°C are a little bit hit-or-miss nowadays, then what is the warmest temperature that we do reliably get in December-February?
Here we're looking at the number of warm days each December-February, going back to 1995.
We can see that we get days above 10°C about half of the time, and some years get two or three of them. Days above 8°C or 9°C are a little more reliable - almost every year has had an 8°C day. But days above 7°C are the only ones that we should really count on, because every year since 1995 has had a least one, and in many cases several.
So going back to Richmond Longley's definition of a chinook, for December-February we don't really see many days in the 10°C range, but 5°C and 2°C are pretty reliable.
Day-over-Day Temperature Changes
Looking at warm winter days is all well and good, but it seems to me that chinooks should be sudden. It's not just about the warm temperatures, but also about the rapid shift from cold to warm. So next we are going to look at how the temperature changes from one day to the next.
Last year a blogger from Calgary named Matt Chernos looked at chinooks in this post: Are the number of chinooks increasing (in Calgary)? Matt mentioned the same difficulty of finding a quantitative definition of a chinook, and he ended up using three measures:
One thing that I do like about the previous warm-days approach was restricting it to December-February. Not that chinooks can't happen in November (we just had a nice, big one this year) but November & March both have plenty of days that are naturally going to be warm, and counting those as chinooks seems like cheating. I want to look for truly unusual temperatures, so I'm going to stick to the real depths of winter.
This chart is a mess, so I'll talk about it really quickly and then move on.
This shows the number of these "chinook" events each year: blue is days with a high of at least 5°C and a day-over-day increase of at least 5°C; green is 8°C with a 5°C increase; and red is 2°C with a 7°C increase.
The data is really noisy though, so lets look at the averages to smooth things out:
And hopefully that's a little clearer. The same mess of data is still shown in the background, but now the 5-year averages have been added on top.
Here we can see that the red and blue lines for temperature jumps up above 2°C and 5°C are fairly close to one another, averaging 3~4 events each year. And the green line for jumps above 8°C is lower, at around 1 per year.
One thing to remember is that here we're looking at chinook "events" - how many times the temperatures jumps up - while in the first chart today it was the total number of warm days. So here we see that in a typical December-January the temperature will jump above 5°C three times, while the earlier charts showed that we would spend a total of 10 days above 5°C.
If a change in high temperatures from -5°C to 2°C or from 0°C to 5°C doesn't sound too remarkable, those are just the minimum ranges. Buried in there are a few really impressive days:
This is the breakdown of the highs above 5°C, and how much the temperature had increased over the previous day. In a lot of cases we can see that the temperature jump was at the 5°C cut-off or less, but there are some days with swings of 10°C, and even a few of 20°C or more.
Getting back to the idea of folklore, the 5 largest temperature swings are shown here. I've broken this list into the Top-5 of all-time going back to the 1880s, as well as the modern ones going back to 1995. We can see the 20°C+ swings in high temperatures, and several of the corresponding night-to-day temperature swings are more than 30°C. That's impressive enough that you might tell stories about it for a few years. (although I have to admit that I have no particular recollection of either February 2nd, 2011 or December 9, 2014).
Scorecard
Here is Edmonton's chinook scorecard for December-February based on just the last 10 years.
So...does Edmonton get chinooks?
If we're only talking about the summer-in-January days above 10°C, then there are some years with one or two, and others with none. But surely all of the days that we get above 2°C and 5°C must count for something?
For today, I'll leave the question open. But next week in Part 2 we'll look at things from a different angle, and will hopefully come up with an answer.
I think that most people in Alberta will be familiar with the term "chinook", but I never know how widely known it is elsewhere? I won't copy the entire wikipedia entry, but the name is a reference to the Chinook people from what is now Oregon and Washington, and a chinook is when air from the west coast spills over the Rockies bringing dry, windy and unseasonably warm winter weather.
The sourthern part of Alberta up through Calgary is famous for chinooks, with temperatures swinging from below freezing to above 15°C in a few hours. That leads to folklore like:
A man rode his horse to church, only to find snowdrifts piled so high that only the steeple stuck out of the snow. So he tied his horse to the steeple with the other horses, and used a snow tunnel to get into the church. Upon his return a few hours later all the snow had melted, leaving the unfortunate horses dangling from the church steeple.That story honestly poses more questions than it answers, but my question is: does Edmonton get chinooks? We don't often see winter temperatures as high as 15°C, but we do certainly see 5°C and even 10°C. Since we're further from the mountains maybe we get baby-chinooks, or chinook-echos?
Just as a caveat, I'm not going to look at the actual mechanism of chinooks, or whether coastal air really does make it's way all the way to Edmonton. I'm just going to look at temperatures to see how often we get changes that could be maybe considered chinook-like.
Today is Part 1 and (spoilers) there won't be any answers. Those will have to wait until Part 2.
To get started, exactly how warm do temperatures have be to qualify as a chinook? Googling around, I can't find an easy answer, so we're going to look at a few approaches.
Warm Days
I found this 50-year-old study online which I'm going to use as a starting point: Richmond W. Longley (1967) The frequency of winter Chinooks in Alberta, Atmosphere, 5:4, 4-16
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| Richmond W. Longley (1967) The frequency of winter Chinooks in Alberta, Atmosphere |
Longley hints at what I'm interested in - we might not get the same warm extremes as the southern part of the province, but we get something. Is it enough to be called a chinook? That paragraph mentions three different temperature ranges:
- 50°F (10°C) - the real chinooks of southern Alberta
- 40°F (4.4°C) - a compromise, where at least there will be some melting
- 30°F to 35°F (-1°C to 1.6°C) - nice enough, but not really something you write folktales about
Here we have the number of days above 2°C, 5°C and 10°C for December-February going back to the 1880s.
For days above 2°C we get between about 15 and 30 days. There have been some low years like 1992-1993 which only had 1, but also years like 2011-2012 with 39, and last winter with 34.
For days above 5°C we get between about 5 and 15 days. And days above 10°C are fairly rare, with many years that don't have any during December-February.
To get a better sense of the trends, here is the same data with the 5-year averages added as dotted lines:
Looking at the averages, during December-February we get about 23 days above 2°C, and about 10 days above 5°C. Those three coldest months of the year have 89 days (90 in leap-years), and so we break 2°C about 25% of the time, and for 5°C it's about 11%.
One thing that stands out here is that the number of days above 10°C has dropped off in the last 100 years - the average used to be 2 or 3 days per year, but now it's down below 1. We actually saw this before, in one of my earliest posts.
Whenever I see strange numbers from a century ago I start to question the data. Edmonton has had a few weather stations over the years (which I talked about here). The first switch happened in 1937, and looking at this chart 1937 is about the point where the frequency of those 10°C days really drops. And when I'd compared the data from the stations, I'd found that the oldest 1880-1937 station was more variable than the newer ones. So it's possible that in the olden-days we really did get more warm days in December-February than we do today, or it's possible that the older data was a little less precise. For now, we'll leave it as a mystery.
If days above 10°C are a little bit hit-or-miss nowadays, then what is the warmest temperature that we do reliably get in December-February?
Here we're looking at the number of warm days each December-February, going back to 1995.
We can see that we get days above 10°C about half of the time, and some years get two or three of them. Days above 8°C or 9°C are a little more reliable - almost every year has had an 8°C day. But days above 7°C are the only ones that we should really count on, because every year since 1995 has had a least one, and in many cases several.
So going back to Richmond Longley's definition of a chinook, for December-February we don't really see many days in the 10°C range, but 5°C and 2°C are pretty reliable.
Day-over-Day Temperature Changes
Looking at warm winter days is all well and good, but it seems to me that chinooks should be sudden. It's not just about the warm temperatures, but also about the rapid shift from cold to warm. So next we are going to look at how the temperature changes from one day to the next.
Last year a blogger from Calgary named Matt Chernos looked at chinooks in this post: Are the number of chinooks increasing (in Calgary)? Matt mentioned the same difficulty of finding a quantitative definition of a chinook, and he ended up using three measures:
- 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
One thing that I do like about the previous warm-days approach was restricting it to December-February. Not that chinooks can't happen in November (we just had a nice, big one this year) but November & March both have plenty of days that are naturally going to be warm, and counting those as chinooks seems like cheating. I want to look for truly unusual temperatures, so I'm going to stick to the real depths of winter.
This chart is a mess, so I'll talk about it really quickly and then move on.
This shows the number of these "chinook" events each year: blue is days with a high of at least 5°C and a day-over-day increase of at least 5°C; green is 8°C with a 5°C increase; and red is 2°C with a 7°C increase.
The data is really noisy though, so lets look at the averages to smooth things out:
And hopefully that's a little clearer. The same mess of data is still shown in the background, but now the 5-year averages have been added on top.
Here we can see that the red and blue lines for temperature jumps up above 2°C and 5°C are fairly close to one another, averaging 3~4 events each year. And the green line for jumps above 8°C is lower, at around 1 per year.
One thing to remember is that here we're looking at chinook "events" - how many times the temperatures jumps up - while in the first chart today it was the total number of warm days. So here we see that in a typical December-January the temperature will jump above 5°C three times, while the earlier charts showed that we would spend a total of 10 days above 5°C.
This is the breakdown of the highs above 5°C, and how much the temperature had increased over the previous day. In a lot of cases we can see that the temperature jump was at the 5°C cut-off or less, but there are some days with swings of 10°C, and even a few of 20°C or more.
Getting back to the idea of folklore, the 5 largest temperature swings are shown here. I've broken this list into the Top-5 of all-time going back to the 1880s, as well as the modern ones going back to 1995. We can see the 20°C+ swings in high temperatures, and several of the corresponding night-to-day temperature swings are more than 30°C. That's impressive enough that you might tell stories about it for a few years. (although I have to admit that I have no particular recollection of either February 2nd, 2011 or December 9, 2014).
Scorecard
Here is Edmonton's chinook scorecard for December-February based on just the last 10 years.
So...does Edmonton get chinooks?
If we're only talking about the summer-in-January days above 10°C, then there are some years with one or two, and others with none. But surely all of the days that we get above 2°C and 5°C must count for something?
For today, I'll leave the question open. But next week in Part 2 we'll look at things from a different angle, and will hopefully come up with an answer.
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