Rare November thunderstorms bring hail to southern Ontario
From freezing rain in Ottawa to thunderstorms and hail in and near the Greater Toronto Area (GTA), southern Ontario experienced some truly interesting weather Saturday.
Rare November thunderstorms rocketed across southern Ontario on Saturday.
If you glanced at the radar, you could have mistaken the month for July. Southern Ontario was treated to a summer-like thunderstorm event as some stronger storms rolled through the area, dropping loonie-sized hail in parts of Brampton, and lighting up the sky from Georgian Bay to Lake Erie.
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Thunderstorm activity this widespread is exceptionally rare in November, but the atmosphere would a way.
Look up: the key to the storms
Temperatures at the surface were pretty seasonal, with the exception of extreme southwestern Ontario where temperatures pushed towards the 20-degree mark. It’s not the classic storm setup, but looking aloft, it’s clear what propelled the storms.
A warm front draped across the region lifted air into a pocket of highly unstable air aloft, a region where temperatures dropped sharply with altitude. The elevated instability allowed storms to grow vertically, with minimal surface heating available this time of year.
The secret ingredient was strong wind shear. The winds aloft turned with height, helping to organize the storms and fuel long-lived updrafts––the kind that’s able to generate larger hailstorms.
Strong wind shear allows a storm to "breathe," providing ideal ventilation to extend the life cycle of a thunderstorm. Those organized updrafts collect supercooled droplets on the ice particles, continuously growing the hailstones.
Low freezing level means the hailstones didn’t have to combat oppressive humidex and warmer ground conditions, ensuring their survival to the ground.
The result was a captivating scene with long-lasting thunderstorms squeezing every ounce of instability out of the upper atmosphere. Even though it felt like a dull, grey day across the Greater Toronto Area (GTA), the upper atmosphere had other plans, generating hail that would be noteworthy in July.
With files from Tyler Hamilton, a meteorologist at The Weather Network.
Stay with The Weather Network for all the latest on conditions across southern Ontario.