Top ten weather stories for 2011: story five

Approaching the end of August, the severe weather season in Ontario had been fairly quiet and tame all summer. With 10 mostly weak tornadoes, incessant lightning and wild wind events in the Ottawa Valley, and a strong tornado in late July in Lambton County, most considered summer’s severe weather to have been pretty much uneventful. Then on August 21, warm, humid air and an unstable atmosphere over the lower Great Lakes created ripe conditions for some active weather. And when a triggering Great Lakes breeze was thrown into the mix, there were the makings for some turbulent summer weather: funnel clouds, blustery winds, hail and tornadoes.

What followed was a wild week of weather that began with a killer twister ravaging the historic town of Goderich on the shores of Lake Huron. During the afternoon of August 21, Doppler radar revealed classic rotating clouds over the lake. Environment Canada had already issued a severe thunderstorm watch that had mentioned the possible formation of severe thunderstorms capable of producing heavy rain, hail, damaging winds and a tornado. Then, at around 3:45 p.m., the weather watch became a tornado warning. Ten minutes later, a severe tornado crossed the shoreline and struck Goderich. The twister’s violent winds blew off roofs, knocked down brick walls, tossed cars, hurled lumber through the air and pulled down large trees. In less than two minutes, the tornado ripped through the heart of the charming, picturesque community with unbelievable damage, killing one person and injuring 40 others. During the subsequent damage survey, meteorologists determined the force of the twister as a Fujita Scale 3 (F3), with winds between 250 and 320 km/h. The length of the tornado track was approximately 20 km, with a width that varied from up to 1,500 m in Goderich to less than 200 m further southeast. The last confirmed F3 tornado in Ontario occurred 16 years ago, on April 20, 1996.

Stunned residents wandered in shock through streets buried in rubble and mangled trees. Trees lay inside houses, while rocks, chunks of cement, thousands of bricks, branches and glass littered the ground everywhere. Once-majestic buildings built 150 years ago lost roofs and upper floors, and structures that weren’t flattened or scattered were shifted off their foundation. Officials placed the town under a state of emergency, blocked access to the downtown and cut off natural gas to damaged areas. Hundreds of citizens had to move in with friends and family, or leave town. The Insurance Bureau of Canada’s estimate for insured damage exceeded $100 million. Ten days later residents could finally turn on lights, take warm showers and talk on their phones. After hitting Goderich, the tornado blew out east of town towards the St. Lawrence River, with wind gusts of 100 km/h, golf ball-sized hail and heavy downpours. In Toronto, torrential rains and gusty winds toppled sailboats, tore limbs from trees and disrupted power. An F1 tornado (peak winds 120 to 170 km/h) occurred in the western part of Gananoque, with tree and minor property damage.

Only three days later, severe weather hit the province again. As August 24 dawned, it became evident that a number of factors were going to coalesce late in the day to trigger severe thunderstorms with the possibility of tornadoes. So electric was the atmosphere that Environment Canada posted a tornado watch at 11:00 a.m. and constantly updated its tornado warnings and watches during the day. The sky darkened prematurely as black storm clouds rolled in, and then lit up with multiple sheet and fork lightning. After 5:00 p.m., thunderstorms came to life east of Lake Huron. For the next six hours, dozens of powerful storm cells rolled non-stop through the province. In the following days, Environment Canada confirmed that three tornadoes occurred on August 24. Two of them – one in the Nairn area to the northwest of London and another in an area between Cambridge and Burlington – were F1 events, while a third in the community of Neustadt in the southwest portion of Grey County was rated F0.

Hydro One reported that 25,000 customers lost power throughout southwestern Ontario and into cottage country. With bursts of lightning crackling at an intensity rate of 1,000 strikes every two minutes, officials in Toronto wisely emptied the stands at BMO Field during a Toronto FC soccer game. At the nearby Canadian National Exhibition grounds, midway rides were shut down as a precaution. In and around Goderich, the threat of a repeat tornado only three days after the last one had hit stoked anxiety levels in the area for much of the evening. Understandably, many of the town’s residents took shelter in their basements waiting for the all clear as thunderstorms lashed the area and skies turned midnight black.