Weather Warning Index

When severe weather threatens, Environment Canada issues weather warning bulletins that notify those in affected areas so that they can take steps to protect themselves and their property from harm. Each year, the Meteorological Service of Canada issues, on average, 15 000 severe weather warnings. A weather warning is an urgent message that severe weather is either occurring or will occur. Warnings are usually issued 6 to 24 hours in advance, although some severe weather (such as thunderstorms and tornadoes) can occur rapidly, with less than a half hour’s notice.

The Weather Warning Index was created to track the performance of Environment Canada’s severe weather warning system in providing Canadians with warnings in sufficient lead time.

The index score for the most recent three-year period, 2010–2012, was calculated to be 7.9 on a maximum scale of 10. This is an increase of 0.4 from the previously reported score of 7.5 for the 2009–2011 period.

The increase is largely due to improvements with respect to providing freezing rain and rainfall warnings in a more timely and accurate manner. Compared to the 2009–2011 period, there was also an overall improvement in the detection of severe weather events for the 2010–2012 period.

Weather Warning Index for a three-year moving average, 2010–2011–2012

Weather Warning Index for a three-year moving average, 2010–2011–2012

How this indicator was calculated

Note: The index reaches 10 if all extreme weather events in targeted areas were preceded by a warning with sufficient lead time, as per the weather warning performance targets.
Source: Environment Canada (2013) Meteorological Service of Canada - Performance Management Systems Division.

The index is calculated based on information from six warning types that are representative of Canada’s climate. These warning types are severe thunderstorm, rainfall, freezing rain, wind, snowfall and marine gale. For each warning type, a component score is determined based on the warning's accuracy in predicting an actual severe weather event and its timeliness in comparison to the lead times identified within Environment Canada warning performance targets.

The index components are calculated using warnings data from a set of selected geographical regions considered representative of the Canadian climate and for which Environment Canada has sufficient warning events information.

The components are an indication of Environment Canada’s performance in providing timely and accurate warnings for each warning type. For instance, the score for severe thunderstorm highlights the challenge of forecasting severe thunderstorms in a timely and accurate manner when compared to other types of severe weather.

The table shows the Weather Warning Index component scores for two three-year moving averages, 2009 to 2011 and 2010 to 2012, by warning type: rain, snow, freezing rain, wind, severe thunderstorms and marine gale. The overall index score for each three-year moving average is also provided.

Weather Warning Index components by warning type, 2009–2011 and 2010–2012
Warning typeRainSnowFreezing rainWindSevere thunderstormMarine galeOverall score
2010–2012 score8.47.37.98.95.88.37.9
2009–2011 score8.07.37.18.74.98.37.5

How this indicator was calculated

Note: The index reaches 10 if all extreme weather events in targeted areas were preceded by a warning with sufficient lead time, as per the weather warning performance targets. The "overall score" is the sum of all the individual weighted Weather Warning Index component scores (consult the Data Sources and Methods for more details).
Source: Environment Canada (2013) Meteorological Service of Canada - Performance Management Systems Division.

Environment Canada’s national weather forecast and warning system relies on several observation networks to detect changes in the atmosphere and the development of threatening conditions. The monitoring infrastructure operates on a 24/7/365 basis and includes 31 weather radar stations, 84 lightning detection sensors, approximately 1300 surface weather and climate stations, 70 weather buoys, 56 automated ship observation programs and 31 stations for launching balloon-borne observations of the upper atmosphere. Also extremely valuable to Environment Canada are hundreds of volunteer weather observers and severe weather watchers from coast to coast.

Weather warnings are invaluable for the protection of life and property and are critical to provincial and municipal emergency measure organizations for managing flood control, sewer overflow and stormwater run-off. Weather warnings are also critical for weather-sensitive users such as snow removal operators and outdoor recreational enthusiasts.

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