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Severe Weather Season About To Begin

In trying to decide what weather tidbit we should look at this week, I hummed and hawed about the ongoing flooding, but decided the regular news is covering that topic nicely. So far this spring has been fairly uneventful, with little in the way of unusual weather. It hasn’t been overly cold and it definitely hasn’t been hot; we have seen some snow and rain, but again, nothing overly noteworthy. What some areas saw last week got me thinking about summer: the first lightning strikes of the season. So I decided to take a look at severe weather, something I like to do around this time of the year. Maybe this will help to usher in some summer weather!

How can you know if a storm is producing severe weather? The answer is not that easy. The first thing is to listen to Environment Canada for watches and warnings. If a watchis issued by EC it means that 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 awarning,this means that a thunderstorm with some or all of the characteristics of a severe storm has already developed and has been confirmed by an eyewitness or radar. This means you should take precautions immediately.

If you’re out in the field without access to a radio, 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; if you can see through it, the storm is likely not severe yet. Lots of lightning or nearly continuous thunder is a good indication of a severe storm. As the storm approaches, keep an eye out for things such as a green sky or mammatus clouds (clouds that look like baglike sacks that hang beneath a cloud); these conditions usually indicate the storm contains huge amounts of water and has very strong up-and-down drafts. 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.

The wordtornadofor most people brings about a feeling of awe and even a little fear. Unless they 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 that occur 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 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.

What are tornadoes and how do they form? A classic definition of a tornado is a violently rotating column of air that extends from a thunderstorm to the ground, and may or may not be visible as a funnel cloud. For this rotating column of air to be classified as a tornado, it must touch the ground.

As to how tornadoes form, the real answer is, we just don’t know. Tornadoes usually develop from super-cell thunderstorms, which are difficult to predict. Even if we were able to accurately predict where and when these thunderstorms would develop, the intense part of the thunderstorm usually only covers an area of a few hundred square kilometres. Within this few hundred square kilometres, the really severe weather may only occur in a small area of maybe 10 to 20 square kilometres. Now, if we look at the size of a tornado, we would find that they range from as small as about 40 metres to as large as two kilometres across, with the average width being around 100- 200 metres. This means that, as far as weather phenomena are concerned, tornadoes are very small. This makes them very hard to study first hand. Unfortunately, this is all the room I have, so more on this next week.


Lookcloselyattheareabetweenthestorm andtheground;ifyoucanseethrough it,thestormislikelynotsevereyet.

About the author

Co-operator contributor

Daniel Bezte

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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