I come from a long line of farmers so it’s very natural for me to always be looking up and around – at the clouds, animals and wind.
When I moved away from the family farm to the East Coast, I was comforted by the thought that I was not alone. I guess when you’re surrounded by water that shapes what you do and when you do it, the weather is top of mind.
Last weekend, I received this interesting email from Mick Ryan who lives on Williams Lake in Halifax.
“Sunday morning at approximately 10:42 and as I look out at the water on our lake I notice the wind patterns acting in a complete perplexing manner.
Normally the winds come from one direction and you can ascertain that direction by simply looking at the ripples in the water. Today, however, the big winds resulted in very large and encompassing fan patterns stretching in a 180 arc. At the same time, there was another pattern occurring in the opposite direction … I can add that it even has confused the ducks who normally float along facing the direction of the winds. However, this morning they were so disoriented, they flew out of the water and took refuge on the lawn, which is something they normally never do. They huddled up against the large trees on the property. Any thoughts on this rare occurrence?”
After I read the email, I assumed the trough reaching back from a snowstorm that was sliding south of Cape Breton must have been directly over Williams Lake, in the Purcell's Cove area of Halifax. A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts. I was anxious to head back to work and to check the charts and the surface weather reports.
Sure enough, between 10 and 11 a.m. Sunday, a cold frontal trough stretched back from the spring snowmaker and across the Purcell’s Cove area.
But there was more… it also sounded like a seiche to me. Seiches are typically caused when strong winds and rapid changes in atmospheric pressure push water from one end of a body of water to the other. When the wind stops, the water rebounds to the other side of the enclosed area. The weather pattern pushes on the water, stacking it at one end, like water in a bathtub. This can take place over any enclosed or semi-enclosed body of water – from a massive lake a small coffee cup.
Last Saturday, the wind had been from the south, it shifted to the north early Sunday morning. The atmospheric pressure dropped rapidly between midnight and 7 a.m. Over the next few hours, the pressure fluctuated quite a bit. At 11 a.m., it took quite a jump.
It looks like the unusual wind and wave pattern on the lake was a combination of seiche that coincided with pressure and wind changes due to the overhead position of a cold frontal through.
Thank you for reaching out Mick. Good luck explaining this to the ducks.
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Cindy Day is the chief meteorologist for SaltWire Network
