Environment and Climate Change Canada (ECCC) along with the Meteorological Service of Canada (MSC) has finally introduced the new polygon warning system across Canada as of this past Monday. The long awaited update follows a similar system that has been used across the United States for over 20 years.

In the past when a severe thunderstorm or tornado warning was issued, it would cover an entire geographically designated watch region, usually related to a County, Regional Municipality or city, as in the case of the Island of Montreal. Very often when a severe thunderstorm warning was issued for Montreal, only a small portion of the city would be impacted, leaving the rest of the population with fair skies. This created a significant trust issue between the system and the public.

As someone who has followed the weather for over 50 years, this would often leave residents confused, and quickly loosing confidence in the weather office. The real threat here would be that the next time the warnings are posted, they could be ignored altogether, at terrible cost. As our climate changes across Canada, this type of approach to warnings was badly needed.

With the new polygon system, forecasters will target areas impacted directly by the approaching storms. The polygons will change quickly as the storms and the threats move along. Thunderstorms and tornadoes are often small in scale and impact very precise regions or neighbourhoods. The hope is that this will regain the public trust in the warning system with fewer "false alarms" being sent out over our cell phones through Alert Ready and on the WeatherCan App. This will also allow forecasters to update and advance the warnings more quickly to those who are in immediate danger from the moving thunderstorm or tornado.

The polygon system will only be used for thunderstorm and tornado warnings. Other weather warnings, and watches will continue to use the current county and municipal boundaries.

So on the afternoon of Wednesday, August 12, when severe thunderstorms were impacting primarily extreme eastern Ontario into far western Quebec, Ile Perrot and Vaudreuil-Dorion, those areas were the only regions that received the thunderstorm warnings. The system worked! The storm dumped 25mm (1 inch) of rain at my weather station on Ile Perrot in under 1 hour, while only 1.4mm fell at Trudeau Airport in Dorval during the same period.