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Continuing with severe summer weather: Tornadoes

The peak tornado months within Canada’s tornado season are approaching

I know in the May 23 issue I said we would take a break from our annual look at severe weather and take a look back at the spring of 2019, then see what the latest long-range forecasts say. It appears I was a little ahead of myself as there are still five days left in the month (as I write this), which means it’s a little too early to try and sum up May’s weather. Instead, we’ll continue our yearly look at severe summer weather by examining the most awe-inspiring weather phenomenon: the tornado.

Before we begin our look at tornadoes I think we have to step back a little bit and discuss: “How can you know if a storm is capable of producing severe weather?” The answer is actually not that easy. The first thing is to check with Environment Canada (EC) for watches and warnings. If a watch is issued by EC it means the potential exists for severe thunderstorms, but they have not yet developed in your area. When you hear there is a watch, you should watch the sky for any development, and if any storms do develop, they have the potential to become severe. If EC issues a warning, this means a thunderstorm with some or all the characteristics of a severe storm has developed and has been confirmed by an eyewitness or radar. This means you should take precautions immediately.

If you are out in the field without access to a radio or the internet, what can you watch out for? First of all, recognize the conditions: how warm and humid is the air? Remember, a moist atmosphere means there is a lot of energy available. Look for a dark or threatening sky — look closely at the area between the storm and the ground, and if you can see through it, the storm is likely not severe yet. Lots of lightning or nearly continuous thunder are good indications of a severe storm. As the storm approaches, keep an eye out for features such as a green sky and mammatus clouds (clouds that look like bag-like sacks that hang beneath a cloud); these conditions usually indicate the storm contains huge amounts of water and has very strong up- and downdrafts. Finally, watch out for any kind of rotation within the storm. This means the storm has become very strong and has the capability of producing a tornado.

Storms quick to form

In this day and age, most of us have internet access nearly 24-7 and if you depend on the weather you usually have one or more weather apps available to quickly check to see what is happening. The best way to know what is going on with a developing thunderstorm is to check out EC radar. While this tool can allow you to see just where a storm is developing and how it is moving over time, you need to remember that thunderstorms can be very dynamic. Storms can develop very quickly, going from almost nothing to a severe storm in less than 20 minutes. Conversely, powerful storms can collapse almost as quickly. Often, when we have an outbreak of severe weather, thunderstorms are developing and collapsing along a line. Radar will show a very strong storm about to hit your area only to have it collapse and weaken just as another storm fires up and becomes severe a few kilometres away. So, while using weather apps and watching radar can be helpful, when severe weather develops and is moving into your area, always prepare for the worst and be thankful if it doesn’t happen.

The word “tornado” for most people brings about a feeling of awe and even a little fear. Unless you have already witnessed a tornado first hand, many who are interested in weather secretly wish they could safely experience the awesome beauty and power of a tornado.

Worldwide, Canada is second only to the United States in the number of tornadoes occurring each year, with an average of about 70 reported. Southern Ontario experiences the highest number of tornadoes, followed by southern Manitoba, Saskatchewan and central Alberta. While these areas report most of Canada’s tornadoes, they have occurred in nearly all regions of Canada.

Tornadoes can strike at any time of the year, but in Canada, tornado season runs from April to October, with the peak months being June, July and August. This differs from the U.S., where tornadoes peak in April and May. This is due to the amount of cold air that is available for severe storm development. In the spring, the southern and central U.S. have become quite hot, but cold air is still closely available to help develop thunderstorms. By midsummer, most of the cold air has retreated well into Canada, putting our region into warm conditions, however, we still have cold air fairly close by to our north.

Unfortunately, it appears as though I’m running out of space to finish up on our topic of tornadoes in this issue. Next week we’ll take a break from the topic of severe weather to look back at how this spring turned out and take a look ahead to see what the latest summer forecasts are calling for. Guess we’ll have to pick up on tornadoes after that.

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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