Things will warm up this week (Wed – Friday), but brace yourself for another cold and cloudy weekend, especially Sunday (6 – 7 degrees below normal) similar to this past Sunday as yet another northerly flow and sinking upper level heights build into Ontario from the north again. This looks to last until about Wednesday – Thursday May 19th.
Here is the GFS upper level heights pattern for Sunday:
So what’s the deal? Well the persistent upper level blocking has been resistant to breakdown, and has been particularly targeting Ontario and Quebec with its cold northerly winds. Despite the long range updates that promised a warm spring, it isn’t all the surprising to have a chilly spring after a strong El Nino. It’s happened in the past, specifically in 1997 after our last strong El Nino. I like to think of it as Mother Nature trying to balance things out after a warm winter. Unfortunately at this point, I would say it means I am wrong on the average May temperature being about 20c, as slightly above normal. We are currently below normal by a couple degrees and with another cold outbreak next week may almost lock in a cooler spring in general.
The good news…things should start to trend near normal for the long weekend in May (around 18c) and there is still hints at some warmer than normal temps in late May.
GFS temps on Sunday May 22:
Also remember we are talking about a general pattern, it doesn’t mean that it won’t temporally break down and you get warmer days in between. Hence the up and down pattern continues. I suspect this will continue until at least mid June until we can finally see the death of this El Nino and it hopefully trends towards La Nina by mid to late summer.