Abstract
ABSTRACT
Western Canada's "severe-summer-storm of the century" is described at length. The maps are based primarily on information from a newspaper survey published one week after the Edmonton tornado. All materials are presented from the point of view of meteorologists. The tornado ravaged areas along the eastern boundary of the city for approximately one hour. It hit the industrial area hardest and was accompanied by extremely heavy rainfall, funnel clouds and two spin-off tornadoes. A swath of giant hailstones, unprecedented for a city in Canada, fell on residential areas. These occurrences, and a windy evening storm, collectively damaged nearly every part of Edmonton on July 31, 1987. For comparison, the research about the Ontario tornadoes of May 31, 1985 is reviewed.
The Atlas includes 11 maps, 3 tables, and 4 previously unpublished photographs. Some of the damaged industrial sites are described in detail using reports from officials and eye witnesses. Responses to the newspaper survey are used to estimate the additional warning time gained by those citizens who were listening to a radio or watching television.
Approximately 30,000 insurance claims for shingle damage by hail were filed. These are investigated by comparing the hail characteristics reported from various communities with the records of two shingling firms. Laboratory research into hail damage to shingles is examined. The hail damage is compared with that of the 1991 hailstorm in Calgary which caused the largest insurance loss for a Canadian natural disaster. However, the Edmonton hailstorm was more severe by most measures.
Many obscure scientific studies and materials related to the Edmonton tornado have been referenced. This study ends with a comparison of the severe thunderstorm risk in Edmonton and Calgary.