Environment and Climate Change Canada began rolling out a polygon-based alert system Tuesday that allows forecasters to draw precise boundaries around severe weather threats instead of issuing warnings across entire forecast zones.
The change applies to thunderstorm and tornado warnings, which will now reach only communities in the direct path of a storm. Until now, colour-coded alerts covered whole regions, often warning people who faced no actual danger.
"This will greatly reduce the areas that would have been otherwise warned when we had zone-based forecasting," said Giselle Dookhie, an emergency preparedness meteorologist with the department. "It reduces those alert notifications if you're not expected to be impacted by that warning."
Real-time storm tracking
Forecasters at the Meteorological Service of Canada can now follow storms in real time, merging or splitting warning polygons as cells evolve and upgrading only the portions of a storm that intensify. Dookhie said the goal is to combat "alert fatigue", the tendency for people to ignore warnings after repeated false alarms.
"We really do want Canadians to take warnings very seriously," she said. "When they do see a threat that's likely to impact them, there is someone behind the scenes checking closely on these storms."
System used in U.S. for 16 years
Anthony Farnell, a meteorologist with Global News, said the United States has used polygon-based warnings since 2007 with measurable improvements in accuracy and lead time.
"If it gets implemented properly, we are going to see some big results quickly as soon as that next severe weather outbreak," Farnell said. "The earlier you can get those warnings out to the people that will be impacted, the more likely you are to save property and then possibly save lives."
The existing colour-coded system will remain active during a transition period to give third-party weather platforms time to adapt. Regional warnings will continue to be used for weather watches, which signal conditions favourable for severe weather rather than imminent threats.
Based on reporting by Global News.