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WeatherWise - Tornadoes

Laurissa Anyas-Weiss, content producer

July 15, 2009 — Tornadoes are the most powerful storms on earth. Each year, Canada sees up to 80 tornadoes while in the US, the number is closer to 800.

Tornado winds have been measured at almost 500 km/h but the strength of a tornado is not based on the speed of its winds. The Fujita Scale is used to measure the intensity of a tornado by rating the amount of damage done to buildings, vegetation, etc. The Scale measures tornadoes from 0 to 5 with a F5 tornado being the most potent tornado.

In Canada, tornadoes are most likely to occur in the BC Interior, in Alberta from the Rockies east across the southern Prairies and into northern Ontario. Through southern Ontario into Quebec along the St. Lawrence River valley into western New Brunswick.

How Tornadoes are Formed

Tornadoes are formed by shearing winds in the upper atmosphere interacting with warm air rising from the surface. This sets up a rotation called a mesocyclone which is essentially a storm within a storm. Down drafts of cold air will cause a funnel cloud to form. A tornado is born when this funnel cloud touches the ground.

Meteorologists know a great deal about how tornadoes are formed but predicting which storms will produce a tornado is still very difficult.

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