Images are circulating on social media of a column of fast-spinning water stretching from lake to the clouds high above a lake just west of Montreal on Sunday.
The images show the weather phenomenon taking shape on Lake of Two Mountains, near Vaudreuil-Dorion, Que. Environment and Climate Change Canada (ECCC) has since confirmed the formation was a waterspout.
“It’s essentially a tornado that forms over water,” said Jean-Philippe Bégin, a weather preparedness meteorologist for ECCC.
The instability created by the body of water and the warm, humid air near the surface helps the waterspout form, he said. It usually happens when cold air systems pass over warm water.
To form a waterspout, wind speeds need to increase with height, creating a vertical wind shear, Bégin said. The shear allows the spinning motion of the air near the water’s surface to stretch upward.
The higher altitude winds can’t be too strong or too weak, or the shape won’t form.
“Waterspouts are usually weaker than tornadoes that form over land,” said Bégin.
They are weaker, but people on water crafts are still vulnerable. Lightning risk can accompany waterspouts and boats could capsize, he said. People on shore should also be cautious, finding shelter if the storm gets close.
“It’s a dangerous phenomenon and it should not be taken lightly,” he said. “Stay away from it. Let it pass. It doesn’t last very long.”
He said a waterspout generally dissipates when it crosses onto land, whereas a tornado that forms on land would not necessarily lose energy when crossing a body of water.
The peak time for waterspouts in Canada is from late July to mid-October, he said.
However, waterspouts are a rare phenomenon. Two waterspouts passed over the St. Lawrence River, near Jacques-Cartier Bridge between Montreal and Longueuil, in 2008.
Bégin said there is no indication that waterspouts or tornadoes are becoming more common in Quebec, but more are being recorded and identified thanks mostly to improved technology and monitoring.
Still, thunderstorms and tornadoes may become more violent because of climate change, he said.