As we hit the second full week of September there has been another Category 4 hurricane to hit the U.S. mainland; this time it was hurricane Irma. Irma made landfall near Marco Island, Florida early on Sept. 10. While the damage inflicted by Irma looks to be significant, the storm will not bring the torrential rains like Harvey did, due to the relatively fast motion of the storm. With hurricane season entering the peak period, we’ll continue to watch the tropics to see what else might be in store.
Now, on to this week’s topic, the summer of 2017 across agricultural Manitoba. If I was forced to use just two words to describe this summer it would have to be average and dry. In fact, when we look at temperatures across the three main centres of Winnipeg, Brandon and Dauphin, it’s surprising just how average it was.
Summer is typically seen as the three-month period encompassing June to August. In this past summer’s data, Winnipeg’s mean summer temperature was 18.5 C, which was bang on the average. Brandon had a mean summer temperature of 17.3 C, which was 0.1 C below the long-term average. Meanwhile, Dauphin had a mean summer temperature of 17.8 C, which was 0.4 C above average. I decided to look at a longer period of time and figured out the average temperature since the beginning of April to see if anything changed. Turns out that both Winnipeg and Brandon were both 0.1 C above their long-term average, while Dauphin was about 0.3 C above average. All in all, from a temperature point of view, summer was pretty darned close to average, with maybe the exception of Dauphin, which was a little above average.
Now on to precipitation. I think everyone could have guessed it has been a dry summer. I know I am starting to see cracks in the soil that are big enough for me to slide my hand into. The question, then, is, “Just how dry has it been?” I looked at the total amount of precipitation that fell during the three-month summer as well as the April-to-August period and created the tables you see here. Table 1 (below) shows the June-to-August period, with total rainfall, followed by the average, with the final column showing the per cent of average. Table 2 (further down) covers the April-to-August period.
For the three summer months, both Winnipeg and Brandon saw similar amounts of precipitation and both stations came in at the low 60 per cent range when compared to average. Dauphin was a little “wetter” as it saw about 85 per cent of average precipitation during the summer. When April and May were added in, we find Winnipeg’s per cent of average stayed the same at 62 per cent and Brandon dropped from 65 down to 60 per cent of average, while Dauphin dropped down to 76 per cent. Looking through the data for all the agricultural Manitoba weather stations for the period of May to August, the driest location I could find was Kane in the central region, with only 43 per cent of average precipitation. The wettest station was Ethelbert in the northwest region, which saw 105 per cent of average precipitation.
What I found interesting — and it makes sense when you look at the totals — was the low number of large rain events this year. Digging through the data of over 60 stations, I counted a total of 16 events that had rainfall totals greater than 40 mm. Over half of these events occurred on either June 14 or on July 22. The heaviest one-day event I was able to find occurred on July 19 when 79.3 mm of fell in Reston. Since I couldn’t find another station nearby reporting any significant rainfall on that date, I decided to check the historical radar images for that area. When I checked out the radar, at first it didn’t seem to be a correct value, as there were no afternoon or evening thunderstorms on the radar images. I then checked to see if there was maybe an early-morning thunderstorm, and there it was. Around 6 a.m. a line of heavy thunderstorms moved through the southwest corner of Manitoba, directly over the Reston area. These storms looked very intense on the radar so I would say that the 79.3 mm at Reston is more than likely legitimate.
So, it was a near-average summer, temperature-wise, and overall, with only a few exceptions, it was a drier-than-average summer. Looking back at the forecasts it would appear no one was able to correctly predict the near-average temperatures, and I was the only one to say near- to below-average amounts of rain. That would mean I get the nod for having the most accurate forecast, but if you check back you might see that my forecast was really just a lucky guess, and even then it was only half right.