When we talk about apparent temperature — what it feels like, we are taking into account the water vapour in the air, wind speed and the actual air temperature. In the winter, we call this measurement wind chill. The explorer Paul Siple first introduced the idea of a wind chill factor in 1939. It indicates the enhanced rate at which the body will lose heat to the air. Our bodies help keep us warm in the winter by trapping a thin layer of air near the surface of our skin. When it’s windy, this thin layer is taken away and additional heat from our bodies is released to try and recreate this layer. This process repeats itself over and over, the higher the wind speed and the faster the warm air is pulled away. In addition, moisture from our bodies is being evaporated, a process that uses up even more heat from our bodies. In 1970 a formula was developed to calculate the rate of heat lost, and in 2001 the wind chill formula was revised into what we see and hear about today.

What still can’t be built into the formula is a person’s physical activity, the sun’s intensity, and the protective clothing being worn. All these things can decrease the cooling effect of those cold winter winds, and this is where the problem seems to arise. What I mostly have an issue with, is how the media uses and reports wind chill.

The biggest problem is that they often don’t understand how wind chill works and tend to apply it to an inanimate object such as a vehicle. It just doesn’t work that way. Objects can only get as cold as the air temperature. If the wind chill indicates that it feels like it is -52 C but the air temperature is -30 C, then the coldest an object can get is -30 C, this includes people. What the -52 C means is that you will be losing heat from exposed areas at a rate equivalent to an air temperature that is -52 C, but once you hit -30 C the object cannot get any colder. So, you or your car might cool quicker, but it won’t drop below the actual air temperature.

OK, now on to our review of last year’s weather. When looking at this, I thought, to make things easier I would put some of the key weather data into a couple of graphs. As you know, I often run out of room writing these articles, and as you know, pictures are worth a thousand words. Also, a lot of us are visual learners — that’s my teacher coming through. I picked one location per province: Winnipeg, Regina and Calgary. If you take a quick look at the first graph you can see how surprisingly similar they are.

The first graph (above) shows the mean monthly temperature for each month (line graph) along with the total precipitation for each month (bar graph). As I pointed out above, the data is very similar across all three locations, which indicates a very similar weather pattern across all three provinces. When looking at the temperatures, two things stand out. The first is that Calgary is much warmer than both Regina and Winnipeg in the winter, but I think most of us already knew that. The second interesting item is that the peak monthly temperature occurred in June rather than July. I think we can all remember back to just how hot June was.

If you jump to the second graph (below), you will see the departure from average temperature for each month. From this you can see that the year starts off warmer than average with temperatures then sliding to well below average in March and April. The big warmup occurred in May, with temperatures rebounding to well above average, and these warm temperatures continued into June. July saw a return to below-average values with the exception of Calgary, which continued with above-average temperatures. Above-average temperatures returned to all three provinces in September before another cool-down in October. Then, as we all can remember, winter didn’t want to move in during November and December and as a result, temperatures returned to well above average.

Looking back at the first graph which shows the total monthly precipitation in 2023, you can again see that with the exception of a couple of months and only one or so stations, total monthly precipitation throughout the year was very similar. The two months that stand out are July and October, where Winnipeg received significantly more precipitation than both Regina and Calgary. If I had included Edmonton, then June would have stood out, as that region received about 150 mm of rainfall. If we look at the second graph which shows the departure from average precipitation, then you can really see how dry the year was. Almost every month had below-average precipitation with only October showing precipitation totals in Winnipeg and Calgary significantly above average.

Overall, 2023 was a warm and dry year across the Prairies. Of particular note was the extreme heat during the second half of May and through much of June. For those who were looking forward to getting out into the heat of summer in July, there was a little disappointment, as cool weather helped dampen things. The question now forming on nearly everyone’s mind is whether the warm, or rather the just dry, weather will continue. After all, a crop has never been determined by the January and February weather. I will take a look at that topic sometime in the next couple of weeks. Next week I think I might have to re-examine just what is a polar vortex since it has once again made the news as it brought extreme cold to the western half of the Prairies and much of B.C. Until then, stay warm!

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It does look like the colder-than-average temperatures will continue for at least one more forecast period. Arctic high pressure will be the name of the game once again, as the weather models predict a large arctic high to begin building southward later this week. To start this forecast period we’ll see a large but weak area of low pressure slide from the northwest to the southeast, bringing with it some clouds, a few flurries and slightly warmer temperatures. The arctic high will begin to push its way into our region Friday, resulting in steady or even dropping temperatures.

By the weekend the high will have dropped southward, placing the centre of the high somewhere around southern Manitoba or Saskatchewan by Sunday or Monday. This is when we’ll see, or rather feel, the coldest air from this system, with overnight lows expected to be around -32 C.

The arctic high doesn’t look like it will move very quickly, with the weather models showing it sticking around for most of next week. Expect daytime highs to be around -20 C, with overnight lows around -30 C.

Further ahead, it looks like warmer weather will try to build to our west, but just how far east it will make it is still up in the air. The models show a large storm system moving in off of the West Coast and this will help to pump warmer air northward ahead of it. The big question is, just how far of an inroad can this warm air make against the arctic high? We’ll just have to wait and see.

Usual temperature range for this period: Highs, -23 to -6 C; lows, -33 to -15 C.

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The first and strongest of what looks to be a series of three arctic highs will slide across the Prairies Wednesday and Thursday, bringing sunny skies and cold temperatures. Temperatures will definitely run at or even slightly below the bottom end of the usual temperature range. Once this high slides off to the southeast Friday, we should see a little milder air work its way in as our winds become southerly on the backside of the high.

A second and slightly weaker arctic high is then forecast to drop southward over the weekend. This will keep our skies mostly clear, but even with the strengthening late-winter sunshine, daytime highs will still be near the low end of the usual temperature range. This high, like all the others, is then forecast to slide to the southeast. This should result in a westerly flow developing across the Prairies late Sunday, lasting into the early part of next week. Temperatures under this westerly flow should moderate toward the middle of the usual temperature range, and we could see a few more clouds.

A third and hopefully final arctic high is then forecast to work southward around the middle to latter half of next week, bringing with it another shot of cold air. Looking beyond this period, there are some hints that the cold pattern we’ve been in over the last couple of weeks will start to change toward a warmer but stormier pattern. After all, we are heading toward March, which can be the snowiest month of the winter!

Usual temperature range for this period: Highs, -16 to -1 C; lows, -29 to -10 C.

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Arctic high pressure building in behind the strong eastern low will keep our skies mainly clear to begin this forecast period. Along with the clear skies will come cold temperatures, with highs struggling to make it to around -15 C. Depending on snow cover, overnight lows will be in the -20 to -25 C range, with the coldest temperatures occurring where the snow is the deepest.

Confidence in the weather models is not that high going into the weekend and beyond, as they try to get a handle on what is looking to become a more active pattern. We could see some snow and blowing snow on Friday as a clipper system moves rapidly across the southern Prairies. Another arctic high will drop down behind this low, bringing clear skies and more cold weather for the weekend. This high will quickly move off to the southeast over the weekend and by early next week we should begin to see temperatures moderate as the winds become more southerly.

We’ll have to watch for the possible development of a fairly strong storm system over the central U.S. around the middle of next week. Currently, the models are keeping most of the energy from this system to our south as arctic high pressure lingers to our north. Once again, confidence in this part of the forecast is low, but it does bear watching.

Usual temperature range for this period: Highs, -14 to 1 C; lows, -24 to -8 C.

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First of all, I don’t think anyone can argue this hasn’t been a cold winter. As we all know, December 2013 was the second coldest on record, with average monthly temperatures running 5 to 7 C below the long-term average. That said, while we did see some really cold days, very few cold records were set during the month. What made the month so cold was that we never really got a break from it!

There are a number of different ways we can compare temperatures to try and determine just how cold it was. One way is to compare just how far we were below average compared to other places on Earth during December. I came across a report that the University of Alabama in Huntsville puts out, that discusses global temperatures and their departure from average. In the report they point out which places or place on Earth had the warmest and coldest temperatures in regard to how much they departed from the long-term average. During December, the coolest area globally turned out to be in central Manitoba, near Lake Winnipeg, where temperatures in the troposphere (the lower part of the atmosphere) were 5.37 C (about 9.7 F) cooler than the long-term average. So, I guess we could argue that we were the coldest place on Earth during December! I then looked at January’s results and found that the coldest region on Earth shifted a little southeastward and was now centred over far-northern Michigan, covering a larger area made up of most of the eastern U.S. and Canada, stretching from just south of Hudson Bay through to the Gulf of Mexico.

The University of Alabama in Huntsville also produces a global map of the monthly temperature anomalies. I have included January’s map here, and if you take a look, you can easily see just how far below average our part of the world is. You can also see that, besides our region, very little of the world saw colder-than-average conditions. Now, before we start crying “Not fair,” we need to remember: eventually this weather pattern that’s giving us these cold conditions will change, and as you can see on the map, we’ll likely switch to a warmer-than-average pattern, given the fact that most of the planet is seeing warmer-than-average temperatures. Also, when you think about it, I think I’d rather have colder-than-average temperatures in the winter, when it’s going to be cold anyway, rather than experiencing them in late spring or summer.

More from the Manitoba Co-operator website: Warm, cold and the polar vortex

OK, now back to looking at the two-month cold snap we are experiencing and how we can determine just how cold it is. I guess the tried-and-true method is to simply go back into the long-term weather records and compare this winter’s temperatures to that of previous winters. I used Winnipeg’s data for this as it has the longest period of record, and when we have cold weather, it tends to affect all regions of southern and central Manitoba. The first thing I looked at was the number of times we’ve seen mean monthly temperatures colder than -20 C. It turns out there have been 80 months going back to 1872 that have been colder than -20 C. When we compare December 2013’s mean monthly temperature of -20.9 C to these months, I found that it falls into 65th place, which means that we’ve seen 64 colder winter months. The most recent cold month was January 2004, which had a mean monthly temperature of -21.7 C. The coldest month ever recorded in Winnipeg was in 1875, when the monthly temperature for January was a frigid -27 C. The second coldest was in January 1966, with a mean temperature of -26.7 C. So, when we look at it from this perspective, December 2013 was not really that cold.

How about if we combine December and January and see how they compare to other years? As it turns out, we don’t see two or more months in a row with really cold temperatures that often. I only counted 11 times in 142 years of data that had both December and January reporting well-below-average temperatures. The last time we had a really cold December-January period was in the winter of 1978-79, when the mean temperature was -20.1 C. This compares to our mean temperature for this winter of -19.9 C. The coldest December-January was in 1886-87, with a mean temperature of -23.1 C. The coldest modern-day winter was in 1949-50 where, thanks to a very cold January, the mean temperature for the December-January period was -21.1 C.

Through February?

If our cold weather continues to the end of February, then it will truly be a cold winter! Looking back, I could only find three winters (December to February) that had all three months reporting below-average temperatures. You have to go all the way back to the winter of 1916-17, when the mean temperature for those three months was -20.1 C. We would have to see this February’s mean monthly temperature come in at -20.4 C to tie this, and with a mean temperature of -21 C over the first eight days, I guess it might be possible. The coldest winter ever recorded was in 1886-87, with a mean temperature of -22.9 C. We would have to have a mean February temperature of -29 C to tie this record, so I think it’s safe to say that this will not be the coldest winter ever.

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By Wednesday of this week the weekend storm system will have pulled well to our east and high pressure will be in place. Wednesday morning will start off pretty cold, with some regions seeing a late-May frost. Temperatures will quickly warm up under the strong late-spring sun and we should see highs in the upper teens to around 20 C.

This high pressure should remain in place right through until at least Saturday, bringing sunny to partly cloudy skies with temperatures warming a couple of degrees each day. On Sunday we could see a bit more cloud and maybe a few isolated showers as a weak area of low pressure drifts through southern and central regions of Manitoba.

Next week looks like it will start off fairly warm, as low pressure begins to develop to our west and an upper ridge develops over our region. This should result in high temperatures in the mid- to upper 20s on Monday and Tuesday. By next Wednesday the weather models predict the western low will push through central and northern regions of Manitoba, dragging a cold front across southern regions. This cold front will likely bring a round of showers and thunderstorms sometime Wednesday.

Looking further ahead, the weather models show fairly typical early-summer weather for the remainder of next week, with high temperatures expected in the mid-20s and the chance of a thunderstorm every couple of days.

Usual temperature range for this period: Highs, 17 to 27 C; lows, 4 to 13 C.

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Winnipeg Brandon

Dauphin

Table 3. 2009 versus 1979, mean C

Jan Feb Mar Apr May Jun Mean C 1979

-27.2

-30.9 -14.7

-16.0 -9.4

-6.9 2.7

1.4 7.7

8.2

Dauphin

2009

1.2

0.3 0.3

Mean C 2009

-18.4

15.6

Mean C 1979

-23.7

-23.3 -10.3

-2.3 7.7

16.3

Recent

-1.7, 1996

-1.4, 1979 -1.9, 1979

Brandon

Mean C 2009

-19.8

-15.6 -10.0

2.9 8.0

10.1

Going way back

-2.4, 1883

-2.5, 1899 -2.5, 1922

Winnipeg

Mean C 1979

-22.5

-22 -9.9 -0.6 7.4

16.2

Mean C 2009

-20.2

-14.6 -7.8

3.2 8.2

10.4

Winnipeg Brandon

Dauphin

-3.5C

-4.1C -3.7C

-5.4C, 1950

-6.5C, 1883

-5.9C, 1979 -6.2C, 1950

-5.8C, 1899 -4.4C, 1936

Recent Going way back

Ithink we have to take a break from looking at thunderstorms and step back and see just how bad the weather has been this past spring and even the past year. I’ve been listening to a lot of people talking about this year’s cold weather and nearly everyone I listen to seems to think that this year has been the coldest start to a year that they can ever remember. Well, I hate to be the party-pooper, but the weather statistics do not seem to agree.

I crunched the numbers a number of different ways and the only period that we are the coldest for is for the first week in June and even then, while we did break some daily records for overnight lows, none of our three main centres (Winnipeg, Brandon, Dauphin) broke any all-time record lows for June. Looking at the killing frost that was widespread across agricultural Manitoba on June 6, 2009, here are the readings that were recorded and how they compared to historical values.

Winnipeg: Coldest overnight low occurred on June 1, 1886, when it dropped down to a bone chilling -6.1C. The overnight low reading of -4.6C on June 6 this year was the latest killing frost ever recorded for the city.

Brandon: They have seen the temperature drop to -3.9C twice: once on June 13, 1969 and then a second time that same year on June 20 – now that’s a late killing frost! The coldest temperature recorded this June was -2.4C.

Dauphin: Like Winnipeg, its coldest June temperature was -6.1C recorded on June 1, 1929. The reading of -4.4C this June was the second-coldest reading for the month, and was the third latest occurrence of a killing frost (other killing frosts occurred June 8, 1982 and June 13, 1969).

No matter which way you look at the start of June, it was just plain cold. Winnipeg seemed to be the coldest of our three main regions during this period as it twice beat its record for the coldest mean daily temperature and also recorded the latest-ever killing frost.

So the first week of June was cold and we know the whole first half of 2009 has been below average; now the question is, has this been the coldest first half of a year since records began? Well, to be short and sweet: not even close. So far for the period of January to June 14 of this year, Table 1 shows us the average values for our three main centres. I have also included a couple of cold years to which we can compare this year, and as you can see, this year is not even close to being the coldest. Remember, we still have a couple of weeks left in June, so our average temperature will increase by at least a half a degree.

Now, maybe some of those really cold years had really cold winters that influence the numbers. While we had a cold winter this year, it wasn’t that bad. So in Table 2, let’s take a look at the actual spring numbers, which are from March to the end of May.

Once again, while we were cold, we didn’t even come close to breaking a record for this period. The most recent year that was at least this cold or even colder was back in 1979. I thought it would be interesting to see how that year and this year compared, and then how the summer of 1979 played out. Have a look at Table 3.

The only month this year that’s colder than 1979 is June, but once again, we still have a couple of warm weeks left and our mean monthly temperature will likely go up by several degrees during that period.

Looking at the second half of 1979, July and September were warmer than average while August was cooler. The October to December period was very cold that year, so let’s hope we see the warm July and September and skip the cool months.

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To understand why different types of precipitation occur, we need to understand that temperatures can vary greatly as we go up and down in altitude. So far in our weather school discussions we have come to an understanding that cold air is heavy and dense, so it tends to sink and stay close to the ground. Warm air is light, and therefore tends to rise. We have also looked at the composition of the atmosphere and when we look at an “average atmosphere” we would expect temperatures to decrease as we move upward.

We now have to skip a couple of lessons and combine these ideas to help explain the different types of precipitation that can occur during the cold months of the year.

A snowflake’s journey

The first and most easily understood kind of winter precipitation is snow. In our part of the world the vast majority of moisture condensing in clouds is doing so in the form of snow. What determines whether that snow will make it to the ground is the temperature of the air that the snowflake has to fall through. If the temperature stays below the freezing point from the cloud to the ground, then we see it fall as snow.

If the temperature on the ground is below zero, but we have a push of warm air that has lifted over the cold, dense air at the surface, then the falling snow can start to melt on its way down to the surface. If the layer of warm air is not very thick, then the snowflake only partially melts before it reaches the subfreezing layer near the surface. Once it reaches this subfreezing layer, the partially melted snowflake then refreezes, turning into an ice or snow pellet. It takes this shape because the outer edges of the snowflake melt in the warm layer, creating a layer of water around the inner core of the snowflake. When the melted snowflake passes through the subf reezing surface layer, this coating of water freezes around the remaining snowflake and creates a hard shell around the soft inner core.

If we take the same scenario as above, but increase the thickness of the warm layer, our falling snowflake will totally melt and become a raindrop. This raindrop will then fall through a layer of subfreezing temperatures. Two things can happen at this point. If the air is cold enough, the raindrop will freeze solid and we will experience ice pellets, but this is fairly rare. What we will usually experience is that the water droplet will cool below the freezing point, but remain in a liquid state (we will discuss why this happens in a later lesson). Once this super-cooled water droplet or raindrop hits an already frozen surface, it will spread out and then immediately freeze, creating what we call freezing rain.

Finally, if the whole layer of the atmosphere between the formation of the snowflake and the surface of the Earth is above freezing, then there is a good chance that the snowflake will melt and remain in a liquid state until it reaches the Earth in the form of a raindrop.

Evaporative cooling

But– oh, you knew there was going to be a “but” – it is never just that simple. Just like when you study humans or animals, the objects you are studying can change the conditions on which the study is based. In this case, the falling snowflakes, ice pellets or raindrops can change or influence the temperature of the air around them, thus changing the conditions.

One thing that can happen is evaporative cooling, which can give us snow when the temperatures in the atmosphere would normally result in rain. If the atmosphere through which the snow falls is not totally saturated – that is, the relative humidity is not at 100 per cent – then the falling snow will start to evaporate as it begins to melt. This evaporative process requires energy, or heat, and this heat is taken from the surrounding atmosphere. This means the surrounding atmosphere begins to cool and eventually it may cool to the point where the temperature is no longer above freezing. Our snowflake will now no longer melt and instead of seeing freezing rain or ice pellets, all we see is snow.

So now you know the difference between all the different types of winter precipitation. Now I wonder just which types we will see from this week’s storm.

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