Hurricane force gusts stir dirt storm in Canada

High winds have downed trees, damaged buildings and fanned at least one massive grass fire in the western Canada province of Alberta.

Striking on Sunday, the windstorm sent a rain of broken glass and rubble onto Calgary city streets, according to CBC News. Acting according to the city’s emergency plan, city officials shut the city core to vehicle and pedestrian traffic.

Data seen by forecasters at AccuWeather.com show that winds gusted to 91 km/h (56 mph) early Sunday afternoon at Calgary International Airport. But much higher winds played along upper reaches of city high-rises. “So even though the wind is currently 50 km/h on the ground, at higher elevations – at the height of the Bow tower – those winds are 149 km/h,” said Bruce Burrell, director of emergency management for the city.

Farther south, powerful chinook winds roared eastward from the foot of the Canadian Rockies. At Claresholm, highest gusts reached 144 km/h, or 90 mph, weather observations showed. Gusts of about 130 km/h, or 80 mph, were clocked between Pincher Creek and Lethbridge in southern Alberta.

A fast-moving grassfire drove at least 125 people from their homes in Lethbridge County, the CBC said. The wind-whipped blaze reached Lethbridge city outskirts before lighter winds allowed it to be brought under control.

The windstorm was of the kind often know as “chinooks”, wherein already strong upper-atmospheric winds gain a boost in speed as the sweep eastward from the foot of the Rockies.

A powerful Pacific storm tracking across British Columbia to northern Alberta was the driver behind the exceptional winds. Over the weekend, this storm also unloaded torrential rain along the B.C. coast, and heavy falls of snow along the Coast Mountains.

 Chinooks

• Chinooks occur when dry west winds, warmed by compression, flow over the mountain ranges and down the eastern slopes toward Calgary.
• The winds can raise winter temperatures from as low as −20 C to as high as 20 C in just a few hours.
• Chinooks blowing off the Rockies regularly reach speeds of 65- to 95 km/h with gusts topping 160 km/h.
• A telltale sign of a chinook is the often beautiful arch — a band of stationary stratus clouds caused by air rippling over the mountains.