Environment Canada’s David Phillips has done a great job summarizing in this article what we have been talking about here; Ottawa and Eastern Ontario’s wet and cool summer.
“No matter which way you cut it, Ottawa has been a soaker in 2017 so far… “Since April 1 to July 11, a total of 102 days, rain has fallen on 71 days… “We live for the weekends,” says Phillips. “Since May 1 there have been 22 Saturdays, and Sundays, and holiday Mondays. Of those 22, only four were dry and none were above 30 C….“The most miserable period (was) from June 15 to July 2. That is a stretch of 18 days. It rained on 18 straight days, honest. It was almost like the water torture test.”
In the article he explains the reason for this is the jet-stream sitting almost directly over the region, which is typically further north this time of year. This is true, however, to expand on that point; the reason the jet stream is stuck overhead is what bigmt and I have been mentioning; the position of the western ridge and an eastern Trough and the Omega Block. With the ridge sitting out west towards the Prairies for the last couple months and trough sitting over the northeastern region, the jet stream is forced to go around these upper atmosphere blocks and the High and Low Pressures that develop in these ridges and troughs.
Like water, the jet stream will take the path of least resistance. This article does a good job explaining the various set ups, as well as this image:
Typically this time of year, the jet stream is usually weak however it is more flat and zonal (keeping the cooler air up north and warmer air in the south) across North America as there is less difference between warm air and cold air. This blocking and extreme dips in the jet stream is typically seen more in the winter months with a stronger differences between cold and warm air.
What is interesting during this set up is that Toronto and Southern Ontario has taken far less punishment than Ottawa and Eastern Ontario. The number of rain days and amounts has been less for Southern Ontario (although still above normal), along with warmer days and more humidity than Eastern Ontario. Most of this is due to geographical regions.
Ottawa sits significantly north and east of Toronto. This results in the Ottawa region not only being influenced by humid weather from the south, but also the Northwest flow and tail end of low pressure systems from Northern Ontario and Quebec. We also tend to get influenced by systems that crawl up the eastern seaboard. This allows our region to see all types of weather with often more rain and snow than other regions, especially during the winter months. Another feature of Ottawa is Cold Air Damming and the valley effect which I will cover in another article towards winter.
Phillips also mentions that we may have to wait until early August to see any improvements:
“Environment Canada’s models show a warming trend in late July and August. That could bring dryer conditions, Phillips says, but don’t put away your umbrella.”
While I am not seeing any big changes in the break down of this trough pattern just yet in the long range, the Euro Weeklies offer a little hope that we see more “normal” (27c – 28c) temperatures rather than below normal for the next couple weeks.