CBC Digital Archives CBC butterfly logo

CBC Archives has a new look: Please go to cbc.ca/archives to access the new site.

The page you are looking at will not be updated.

Why can’t we predict tornadoes?

The Story

Almost every tale of tornado tragedy begins like this: "It came without warning..." Despite all the advances in technology over the last century, meteorologists still can't tell when or where a tornado will strike. The best they can do is to warn Canadians about conditions that may or may not spawn a twister. As we hear in this clip, Environment Canada's weather office is forever walking a fine line between crying wolf and being ignored. 

Medium: Radio
Program: Cross Country Checkup
Broadcast Date: March 29, 1998
Guest(s): Ian Rutherford
Host: Lucy McNeill, Stan Gibbons
Duration: 6:43
Photo: National Climatic Data Center HSEI

Did You know?

• Though tornadoes themselves are hard to predict or track, Environment Canada uses many tools to monitor cloud systems and severe thunderstorms that can produce tornadoes.
• Ninety-five per cent of Canadians live in areas monitored by microwave weather radar stations. Each station scans a 325-kilometre radius, although the optimal range for detecting thunder clouds is 30-120 kilometres.

• There are two types of weather radar: conventional, which shows the location, intensity, type and amount of precipitation; and Doppler, which indicates the direction and speed at which the precipitation is moving.
• Tornadoes themselves are too small for Doppler radar to see, though it can detect the wind patterns that tend to produce them.

• Satellites also take pictures of cloud formations day and night, and can detect severe thunderstorms that occur between radar stations or beyond their reach. Again, tornadoes are too small to show up on the imagery.

• Because tornadoes are so unpredictable, short-lived and localized, the most valuable tool available to Environment Canada is a nationwide network of volunteer weather watchers. These observers (many of them are farmers) call the weather office when they spot tornadoes or severe storms.

• Using information gathered by all these mechanisms, Environment Canada's weather service each day produces 1,300 public forecasts for 200 regions, as well as 1,000 aviation forecasts for 175 airports. They are heard daily by 90 per cent of Canadians.
• Environment Canada issues weather advisories for the following conditions: severe thunderstorms, tornadoes, freezing rain, heavy rain, frost, wind, marine wind, dust storms, blizzards, heavy snowfall, winter storms, windchill and cold waves.

• There are three kinds of advisories issued by Environment Canada:
- A "weather watch" alerts people to conditions favourable to the development of severe weather.
- A "weather warning" indicates that severe weather is occurring or that hazardous weather is likely.
- A "weather advisory" indicates occurring or expected weather that may cause general inconvenience, but doesn't pose a serious threat.

• The total number of tornadoes reported in Canada has increased over the past half century, according to a 2000 university research study called "Canadian Tornado Climatology for the period 1950 to 1997." In the 1950s only 177 tornadoes were reported, but in the 1980s the number shot up to 630. However, the author notes that since climatic conditions haven't changed significantly over this period, the trend is probably an indication that tornadoes are being observed, reported and recorded better than in the past.


Deadly Skies: Canada's Most Destructive Tornadoes more