Friday, 20 December 2013

2013 Thunderstorm Stats Across Canada

July 15 south of Regina, SK, one of the biggest tornado outbreaks of the year. Chase team: @steinbachwx, @lovestormsmb & I (@jjcwpg)
     In this post, I will be talking about severe thunderstorms and tornadoes across Canada this year. This is the 4th year that I have been gathering such stats. However, this year I have added a new set of data: a comparison of thunderstorm days among 42 select cities across the country. A summary of how I gathered all these stats can be seen here. Thank you in advance for taking a few minutes to read this post! Note that I have made the maps quite large to make it easier to see the finer details. As a result, this post looks a lot of longer than it really is!

     Let's start off with severe thunderstorm warning days across the country. The following map shows the number of days that severe thunderstorm warnings were issued across Canada this year. Note that I have merged some warning box zones in BC, Manitoba, and eastern Canada. I did this because the warning boxes are generally larger in Alberta and Saskatchewan than in other provinces which would give them a higher frequency bias. By merging zones in other provinces, their sizes become closer to the size of the boxes in Alberta & Saskatchewan, reducing the bias somewhat (but it is impossible to be perfect).

     However, click here if you wish to see the map with the original warning boxes (with no modifications/merges).

     Because I did not make this type of map last year, I cannot really compare this map to last year. Either way, it is quite noticeable that the busiest areas for severe thunderstorms this year appears to have been southern Alberta, parts of southern Ontario and southeastern Québec. The highest frequency of severe thunderstorm warnings was in extreme southwestern Ontario, in the Windsor-Chatham-Sarnia region where 25 days had severe t-storm warnings. Second place goes to the areas east of Montréal and east of Calgary where 22 days had severe t-storm warnings.

     The following map shows the number of tornado warnings per warning zone this year:

     A map of confirmed tornadoes by Environment Canada can be seen here. Note that many tornadoes went unconfirmed or unreported this year, as occurs every single year.

     The strongest tornado this year was an EF-2 near the small hamlet of Glenarm, Ontario on May 21. As of today, there have been 22 confirmed tornadoes in Ontario this year, which is well above the normal of 12 in a year. However, the large number is likely due to increased reports and surveys rather than an actual increase in the number of tornadoes. In addition to the EF-2, 5 EF-1's were confirmed across Canada this year, 4 in Ontario and one in New Brunswick.

     One of the latest tornado events on record occurred near Prescott, Ontario, south of Ottawa on November 23. A farm silo was significantly damaged. It was rated an EF-1. According to Environment Canada, it was the 3rd latest tornado on record in Ontario. Other late season tornadoes in the province included the Exeter tornado of December 12, 1946, the Leamington tornado of November 29, 1919, and the Hamilton tornado of November 9, 2005. It wasn't the strongest tornado ever recorded in November in Canada; an F-2 tornado struck near Mont-Saint-Hillaire, Québec on November 16, 1989. However, it might have been the strongest tornado for so late in the season. Unfortunately, I have not been able to find a reliable source of tornado data for Canada, and therefore I cannot confirm this.

     Follow this link for a list of the biggest tornado outbreaks of 2013 across the country.

     In total, there were 122 severe thunderstorm warning days and 28 tornado warning days across the country this year. This is actually very similar to last year when between 110 and 120 severe t-storm days and 30-35 tornado warning days occurred. The next graph shows the number of severe t-storm days and tornado warning days per province in 2013:

     This year there was a 3-way tie between Alberta, Saskatchewan and Ontario for the most severe thunderstorm warning days, at 59 days. Manitoba placed fourth with 45 such days. Everyone but PEI and Ontario saw an increase compared to last year.

     The last map I have for you is a new dataset that I have added this year. The number of thunderstorm days in 42 select cities across the country:

     Windsor, Ontario saw the most thunderstorm days this year with 41 thunderstorm days. Red Deer, Alberta came second at 34 thunderstorm days. Unfortunately, I have not been able to gather historical statistics on thunderstorm days outside of Winnipeg yet, therefore I cannot compare this year to the past at this time. Of note, these thunderstorm day stats were obtained using METAR which allowed me to include thunderstorms that occurred in between hourly observations. As a result, no thunderstorm days were missed.

     Hopefully you enjoyed this post! Thanks for reading!

     The top 10 weather events/stories of 2013 for the Winnipeg area are to come around New Year's! Be sure to take part in my latest poll: What do you think were the top 2 weather stories of 2013 in the Winnipeg area?


  1. For anyone with travels on Christmas Eve (like me), keep in mind a clipper system will likely be bringing us some snow. Although it will bring some milder temperatures, the snow is definitely not very good news for travellers. At this point, anywhere from 2-8 cm or so is predicted by models. We'll see how that evolves in the next couple days...

    Another super-cold night possible early Monday. I would not be surprised to see lows in the -34°C to -36°C range, thanks to mainly clear skies and light west-northwest winds. GEM weather model has been giving us lows near -38°C. Will be interesting to see how low we get.

  2. Incredible cold in northern Saskatchewan this morning with lows in the mid -40's. Low as of 6 am was -45.4°C in Stony Rapids.

  3. The ice storm in southern ontario is looking really dangerous, hopefully my family in London will be ok. Ice storms are one thing southern Mb dos not get much of. JJ, do you think My plain tomorrow afternoon to Toronto to visit family will be canceled because of the ice storm?

    1. Oh my, well I'm guessing there will definitely be delays. I can't speak for the Toronto airport wether there will be cancellations, but it wouldn't surprise me if there were some. I wish you a safe and great trip though!

    2. Thanks, I shouldn't have expected you to know if my plain would be canceled! I'll try to phone West jet.

    3. Yes that would be a good idea. That ice storm sure didn't come at a good time with all the holiday travellers!

  4. One other chart you might view is used on NWS Chanhassens Top Ten Weather events Done by SPCshowing severe drop in tornado reports..Don