About 15 tornadoes are verified in Alberta every year, with undoubtedly many others that are unobserved or unreported. Canada uses the Enhanced Fujita Scale (EF-scale) that rates tornadoes from 0 to 5, based on wind velocity and damage left behind. A tornado with a 0 rating inflicts light damage, followed by moderate, significant, severe, devastating and finally, at stage 5, incredible damage. For obvious reasons, it is easier to measure damage indicators than wind velocity.
Warning signs of a tornado are:
- Severe thunder and lightning
- Extremely dark sky
- Green or yellow clouds
- Rumbling or whistling sound
- Rotating cloud base
- Debris in the air
- Sudden calm after heavy rain and hail
- Agitated pets or livestock
It is best to err on the side of caution if some, or all, of these conditions are present. Don’t wait for a funnel cloud to touch down and don’t chase the storm in hopes of getting some good photos. Take cover in your pre-planned safe spot, preferably in the basement of a solid building or in an interior room without windows. Time permitting, close all windows and doors. Wind speed is magnified when funneled through a small opening, and high winds inside a building can turn household objects into missiles. Most injuries during tornadoes are caused by flying debris.
Experts disagree on the wisdom of remaining in your vehicle should you meet a tornado while driving. Naturally, you will drive in a direction away from the storm, but if debris and poor visibility force you to stop, one course of action is to remain in the vehicle with seatbelt fastened and head down lower than the windows. At your discretion, leave the vehicle and find a low place on the ground where you can lie flat with arms protecting your head. Be prepared to move quickly as heavy rain may cause flooding. Whether in your vehicle or outside, stay away from power poles and trees.
A family emergency plan should include discussions about warning signs of a tornado and appropriate actions in the event of one of these awe-inspiring and extremely dangerous storms. Watch for storm warnings on weather websites, subscribe to emergency warnings on social media, or download an app, available from The Weather Network or Alberta Emergency Alert.