What's behind Atlantic Canada's ferocious winds?
Under the right conditions, typically amid a fall or winter storm, both the Cape Breton Highlands and southwestern Newfoundland can be blasted by wind gusts as high as 200 km/h. That's as strong as the wind in a Category 3 hurricane.
Les Suêtes and Wreckhouse winds are both, in part, a product of the region's unique topography and its position at the eastern tip of North America.
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WHAT CAUSES LES SUÊTES WINDS?
The Cape Breton Highlands are the site of Les Suêtes, a name that derives from the French "sud est," describing their origin. The winds sweep out of the southeast over the plateau of the highlands -- about 480 metres above sea level -- and go screaming down to the Gulf of St Lawrence.
Though they can occur at any point in the year, Les Suêtes are most common in the winter, when the Maritimes and Newfoundland are often on the receiving end of rapidly-intensifying low pressure systems from the U.S. Northeast, including the infamous 'weather bomb'.
The downsloping effect is an essential component in making Les Suêtes so potent, but the ocean and the gulf also play a role. With the Gulf Stream off to the east and the chilly Gulf of St Lawrence off to the west, Cape Breton sits positioned between a very strong marine temperature gradient. That, in turn, sets the stage for a strong temperature inversion -- that is, a layer of warmer air sitting atop a colder layer.
WATCH BELOW: THE SET UP FOR A LES SUÊTES EVENT
While the inversion is well above sea level, it frequently ends up close to the same height as the highlands themselves. That gives the southeasterly flow only a narrow space to squeak through between the terrain and the 'capping' layer of the inversion. It's a bit like putting your thumb over the end of a hose. If you narrow the opening without reducing the amount of water flowing in, and the water flowing out has to move faster.
Most winters see several episodes with wind gusts higher than 90 km/h, and gusts up to 150 km/h generally happen at least once per year. Les Suête events typically last for 3 to 6 hours, but can be as short as 1 hour, or linger for 12 or more.
During these episodes, driving along the Cabot Trail -- especially in high-profile vehicles -- can be treacherous. Damage to buildings and toppled tractor-trailers have also been reported.
A similar effect happens on the southwestern tip of Newfoundland, home to the Wreckhouse winds. Thanks to slightly higher mountains and the fact storms are generally more developed by the time they reach Newfoundland, Wreckhouse winds can be even stronger than Les Suêtes.
Sources: AMS |
