Alexandra Pope, staff writer
April 10, 2011 — Golf ball-sized hail dented cars in parts of southwestern Ontario Sunday morning as an intense thunderstorm moved across the region.
Environment Canada rolled out severe thunderstorm warnings from Goderich to Hamilton as the storm pushed into southwestern Ontario around 9 a.m.
One intense cell generated brief periods of hail ranging from pea-sized to golf ball-sized in Goderich, Stratford, Hensall, Seaforth and even the Tri-City area.
In Mitchell, north of Stratford, hailstones smashed through the plastic moulding around the windows of David Hafner's truck and dented vehicles throughout the community.
“Our house walls were vibrating during the thundering onslaught,” Hafner said.
“Roads were three inches deep in (hail) in minutes.”
The storm was the result of a weather phenomenon called a mesocyclone, in which a thunderstorm becomes so intense and organized, it can sustain itself for long periods of time without drawing upon midday heat for energy, explained Rob Davis, a meteorologist at The Weather Network.
This particular storm formed west of Lake Michigan on Saturday afternoon and kept going for more than 12 hours before finally fizzling out near Hamilton.
“Temperatures were warm and the dynamics were there in the northern United States for a thunderstorm to develop, and once it did, it was self-sustaining all the way through southern Ontario,” Davis said.
“Mesocyclones are one of the most common ways to get an early morning thunderstorm.”
The same system that generated the mesocyclone also produced severe thunderstorms in Iowa, some of which spawned tornadoes. One massive twister devastated the town of Mapleton Saturday night.