Weather radar is a prime tool of Environment Canada in detecting heavy precipitation, rapidly developing cloud systems and other signatures of severe thunderstorms, which can spawn tornadoes. Weather radars cover the areas inhabited by 95 percent of Canada's population. Each radar scans a radius of about 325 km, although the best range for detecting thunder clouds is 30 to 120 km.

Just as a searchlight beam picks out and reflects off an object, weather radar sends out microwave pulses that bounce off rain, hail and snow. The radar measures the pulses reflected back by precipitation and relays the patterns to a video screen for a meteorologist to interpret.

Conventional weather radar can show the type, amount and rate of precipitation. Doppler radar, can also measure the speed at which precipitation is moving in the area the radar covers. While the actual tornado is usually too small for the Doppler radar to see, it does detect wind shifts, gust fronts and cyclonic patterns that are the signature of tornadoes.

Satellites

Day and night, satellites send pictures of cloud formations over large areas of the globe. They can also detect what is happening between weather stations and radar sites. For instance, severe thunderstorms, the parents of tornadoes, are usually less than 80 km across and Satellites can often detect them even if they are out of radar range.

Combined with radar data and conventional observations, satellite imagery can provide a complete picture of developing thunderstorms and tornadoes.

Volunteer Weather Watchers

All across Canada, thousands of volunteers watch the skies. When they spot tornadoes, thunderstorms, or other severe weather, they report it to Environment Canada.

Tornadoes and severe thunderstorms can wreak tremendous havoc, even though they occur in comparatively small areas for short periods. Forecasters’ technological aids can meet their limits in severe weather situations. Satellites can't resolve enough detail to see individual tornadoes and radars can only detect what lies within their range. When such small, rapidly forming phenomena as tornadoes surface, on-site observations are essential. Timely and accurate observations of severe weather from our volunteers are an invaluable addition to Environment Canada's observation network.