Top ten weather stories for 2009: story nine
9. Winds Plough Through Alberta
On first look, severe summer weather across the Prairies appeared less frequent and less energetic in 2009, especially compared to the previous two very active summers. Undoubtedly, the enduring cold had something to do with it. Westerners witnessed only 17 tornadoes compared to the normal 33. Total severe weather events, including tornadoes, heavy rain, wind and hail, numbered only 189 across the Prairies – less than the recent 20-year average of 221 events, 131 fewer than last summer and less than half the 410 events in 2007. The one exception was severe wind, especially in Alberta, where the number of wind events was more than two times the 20-year average.
Extensive property destruction was the work of violent wind gusts often moving 15 to 20 km ahead of the main storm. Also called plough winds, these strong, sudden downdrafts bring cool, dense air from aloft, rapidly spreading it outward ahead of the thunderstorm or squall line. Plough winds often strike a larger area than tornadoes but can be just as strong. Straight-line winds are fairly common in the west, inflicting more property damage than tornadoes. One such wind blasted through Edmonton on July 18, toppling hundreds of trees and knocking out power to tens of thousands of customers. Wind gusts that clocked at 106 km/h ripped large branches from trees, throwing them about like toothpicks as spectacular lightning zigzagged across the sky and marble-size hail fell. A wind sensor mounted on a tower east of Edmonton recorded a gust speed of 134 km/h moments before snapping the tower in half. Another powerful wind storm on September 28 also took down hundreds of trees in and around the city. It was one of the worst years ever for Edmonton’s urban forest. In both storms, city golf courses and parks were closed as crews worked for days clearing downed trees from fairways and trails.
The summer’s most spectacular wind storm occurred on August 1 when a 200-km-long weather system, albeit discontinuous, roared across much of Alberta accompanied by heavy rain and hail. Just ahead of the “weather” was a gust front or plough wind packing winds in excess of 100 km/h. Environment Canada issued watches and warnings across central Alberta during most of the day. The strongest reported winds were 141 km/h at Three Hills and 125 km/h at Red Deer. Between 5 p.m. and 6 p.m., “hurricane-like” weather broke loose in Stony Plain west of Edmonton and in Camrose, disrupting outdoor festivals and country concerts. At the site of the Big Valley Jamboree in Camrose, violent winds shook the performance trailers and flattened the main concert stage where up to 100 people stood. Thunder, lightning and heavy rain continued to pummel the site as emergency crews worked frantically to rescue those trapped under twisted lumber and dangling steel. One person died and 75 were injured. First thought to be a tornado because of its sound and force, it was later confirmed as a freakish plough wind. Not finished yet, the same weather system was in Calgary two hours later where it roared through the downtown, scattering debris and cutting power. Wind gusts blew bundles of steel rods from the roof of a construction site 40 m to the street below where it tragically struck a family of four, killing a 3-year-old girl and injuring her brother and father.
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