July 9, 2013 – TORONTO, CAN – It is official: the epic rainfall in Toronto on Monday afternoon that drenched highways, had cars bobbing up and down in rainwater and overwhelmed 911 was an extreme weather event. No, experts say, it wasn’t because of climate change. But yes, we will likely see more storms like it. “This is likely the wettest moment in Toronto’s history,” David Phillips, senior climatologist with Environment Canada, said on Monday evening while rain was still falling. “By the end, we may have a new all-time one-day record.” More than 90 millimeters of rainfall was recorded at Pearson International Airport in just two hours, starting at about 4:30 p.m. To put it in perspective, the wettest day in Toronto was Oct. 15, 1954, when Hurricane Hazel slammed the city and 121.4 millimeters of rainfall was recorded over the entire day. The wettest July day in the city was July 28, 1980, when 118.5 millimeters of rain fell — again, over the entire day. July usually gets about 75 millimeters of rain in the entire month. That’s why Monday’s rainfall was epic. “All of that rain, it fell in less than two hours,” Phillips said. “It’s just incredible.” Brian Edwards, a meteorologist with forecasting service Accuweather.com, said a cluster of extremely slow-moving thunderstorms was responsible for the deluge. “It was almost as if the system refused to move . . . it stood there and rained and rained,” he said. “Nobody could have guessed at the amount of rain it would unleash.” Flooding was inevitable, Edwards said, adding that no infrastructure can possibly handle that kind of rain. But Phillips points out that Toronto, like other cities, is becoming more vulnerable to flooding as more of it is covered with asphalt. Building materials are impervious to rain and so “we end up with flash floods,” he said. Making things worse, the ground had still not absorbed all the water from earlier storms by the time the big downpour hit, so there was nowhere for the rainwater to escape.
Phillips says we are not finished yet — there is “another line of thunderstorms coming our way.” Are there similar extreme weather events in Toronto’s future? Phillips says Monday’s rainfall wasn’t due to climate change, “but it is consistent with what we may see in the future: heavy rains in short periods. Nature is giving us a preview of what we may soon see.” As temperatures rise globally, so do the chances of extreme weather. The United Nations Intergovernmental Panel on Climate Change said in its 2012 report that short, powerful rains, hurricanes, heat waves and droughts will intensify. By the end of this century, the average global temperature could rise anywhere between 1.6 and 4.4 degrees C, it said. Closer to home, a report from the Toronto Environment Office released late last year predicts dramatic changes in weather between 2040 and 2050. –The Star
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