Edmonton tornado
| F4 tornado | |
|---|---|
| Formed | 31 July 1987 |
| Dissipated | 31 July 1987 |
| Lowest pressure | 919.3 mb (27.15 inHg) |
| Max rating1 | F4 tornado |
| Duration of tornado outbreak2 | 2:55 p.m. to 8:00 p.m. MDT (14:55-22:00UTC) |
| Highest winds | |
| Largest hail | Tennis ball and larger |
| Maximum rainfall | 300 millimetres (12 in) |
| Damage | $332.27 million ($615 million in 2017 dollars) |
| Power outages | Yes |
| Casualties | 27 fatalities 253 injuries |
| Areas affected | City of Edmonton, Edmonton Capital Region, Central Alberta |
|
1Most severe tornado damage; see Fujita scale 2Time from first tornado to last tornado |
|
1Most severe tornado damage; see Fujita scale 2Time from first tornado to last tornado
The Edmonton tornado of 1987, an event also known as Black Friday to Edmontonians, was a powerful and devastating tornado that ripped through the eastern part of Edmonton, Alberta, Canada and parts of neighbouring Strathcona County on the afternoon of Friday, July 31, 1987. It was one of seven other tornadoes in central Alberta the same day.
The tornado remained on the ground for an hour, cutting a swath of destruction 30.8 kilometres (19.1 mi) long and up to a 1,300 metres (0.81 mi) wide in places, and peaking at F4 on the Fujita scale. The tornado killed 27 people, injured more than 300 people, destroyed more than 300 homes, and caused more than CAD332.27 million in property damage at four major disaster sites. The loss of life, injuries and destruction of property made it the worst natural disaster in Alberta's recent history and one of the worst in Canada's history.
Weather forecasts issued during the morning and early afternoon of July 31, 1987 for Edmonton revealed a recognition by Environment Canada of a high potential for unusually severe thunderstorms that afternoon. Environment Canada responded swiftly upon receipt of the first report of a tornado touchdown from a resident of Leduc County which is immediately adjacent to Edmonton's southern boundary.
In the week preceding July 31, a low pressure system sitting over southwestern British Columbia fed warm, humid air into central Alberta. Daytime heating along with near-record dewpoints over Alberta triggered a series of strong thunderstorms that persisted throughout the week. On July 31, a cold front developed over western Alberta, colliding with the warm moist air that persisted over the region. Forecasters recognized the elevated risk for severe weather early in the day. Weatheradio broadcasts and interviews with the media stressed "vicious thunderstorms" and "extremely strong and violent thunderstorms".
Severe thunderstorms developed rapidly over the foothills early in the day and quickly moved eastward. The first severe weather watches were issued over central Alberta late in the morning and continued early in the afternoon. At 1:40 PM, a severe weather watch was issued for the Edmonton area, including Leduc County, Parkland County, and Strathcona County. The watch was later upgraded to a warning at 2:45 PM as the line of storms approached the area. As the cluster of storms approached the Leduc area, a violent cell rapidly developed ahead of the main line of storms and sharply turned northward.
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