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A record-breaking heat wave

It’s not yet clear whether we’re done with these summer hot spells

In the last article we began discussing summer temperatures across the Prairies, and the warm/hot daytime high temperatures we’ve seen since mid-May. It seems like Mother Nature decided to pipe in by bringing one heck of a record-breaking heat wave to the southern and central Prairies from Aug. 10 to 12.

Just what brought the record heat to our region? Earlier last week, an upper ridge of high pressure began to develop over the southwestern U.S. and began to spread northward. This ridge diverted the subtropical jet stream northward, which resulted in subtropical air moving into our region, especially in the low to mid-atmosphere. This meant that the air mass over a large portion of the Canadian Prairies had a very warm and deep layer of air over top of it. The strong ridge of high pressure that was in place meant that the air was undergoing large-scale subsidence, or sinking. Sinking air accumulates at the surface and is compressed, causing the air to heat up. Combine this heating through compression with air that was already very warm to begin with, and you get record-warm temperatures.

If I was to list all the daily records that were broken across the Prairies during this period I would end up taking a whole page. So, to bring down the numbers a little bit, I have only included the all-time-record highs that were broken — and yes, that means that those stations recorded their hottest temperatures since records began for that region, no matter what month. Then, I listed the all-time-record highs for the month of August that were broken. You will notice that the hottest temperatures occurred over Alberta and southwestern Saskatchewan. Thanks to a little more wind, and higher humidities, temperatures across Manitoba were a few degrees cooler. The higher humidities and hot temperatures Manitoba saw on Sunday resulted in very high humidex values. The highest humidex I was able to find was in Winnipeg, when the temperature hit 35.3 C and combined with a dew point of 22 C, resulted in a humidex temperature of 45 C. While this value wasn’t record breaking, it was the hottest apparent temperature measured during this heat wave. The hottest absolute temperature I was able to find in Manitoba was 39.1 C, which occurred at Morden on Sunday.

Table 1: New August all-time record highs set in 2018 (degrees C).

Table 2: New August all-time record highs set in 2018 (degrees C).

I guess the next question now is whether we will see more record-breaking heat, or are we going to have to “pay back” Mother Nature with a period of cold weather? Personally, I think we are not yet done with the heat, but as we all know, Mother Nature loves to prove me wrong.

About the author

Co-operator contributor

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.

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