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Watches, warnings, wind and tornadoes

tornado in saskatchewan

June, July and August are the peak months for tornadoes in Canada

In the last issue I said we would continue our look at severe summer weather by looking at wind. Most of the time when we talk or worry about high winds, those winds are associated with thunderstorms. So, in this issue we will begin our look at winds and thunderstorms by first examining the most awe-inspiring weather phenomenon: the tornado.

Before we get to that, I think we must step back a little and discuss how you can know whether a storm is capable of producing severe weather. I was out walking the other day when a thunderstorm was approaching and there were several people around who had no idea how to tell whether the storm was potentially dangerous or even if it was coming in their direction. The answers to these questions are often not that easy, but there are definitely some things to look for.

Of those, the first 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 of the characteristics of a severe storm has already developed and has been confirmed by eyewitness or radar. This means you should take precautions immediately.

Next up, 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 is a good indication of a severe storm. As the storm approaches, keep an eye out for features such as a green sky or mammatus clouds (clouds that look like bag-like sacks that hang beneath a cloud); these conditions usually indicate that the storm contains huge amounts of water and has very strong updrafts 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.

In this day and age, most of us have phones with 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, and whether it may affect your location, 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 severe 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 does not happen.

Also, on a side note, it does not matter what weather app you are using; the radar data comes from Environment Canada, so one app is not going to show different radar data, just different ways of displaying the data (I recently got into an argument with someone over this).

Tornado season

Now on to winds and tornadoes. 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 U.S. 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. 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 close by to our north.

Unfortunately, it appears as though I am running out of space to finish up on our topic of tornadoes in this issue. Next week we will take a break from the topic of severe weather to look back at how this spring turned out and look ahead to see what the latest summer forecasts call for. Guess we will have to continue our look at tornadoes and damaging winds in the next issue after that.

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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