Lake Superior Seiches
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Hi, I'm Dave Thurlow from the Mount Washington Observatory. Yesterday on The Weather Notebook I was talking about seiches, seiches being wave systems in lakes and bays caused by just the right combination of weather systems. Winds an pressure hold the key to sieches whose waves have actually killed people. But seiches aren't always so dramatic, as producer James Jones explains:

JJ: Lake Superior is huge and sharp differences in barometric pressure on different ends of the lake are fairly common. That means the lake is subject to seiches, and people who live and work around the lake will tell you that in some rare instances, the impacts are dramatic.

Gregg Bruff works for the Pictured Rocks National Lakeshore. He remembers seeing the effects of a seiche one day he and his colleagues decided to check things out after a heavy thunderstorm.

GB: "We drove down the road to inspect some of the tree damage and on the way back we noticed that Lake Superior was down a lot. And there's a beach here at Sand Point and there was no water on the beach. In the shallow areas it was just completely dry. And that's when we went over to the patrol boat and noticed it was sitting on the bottom. Normally there would probably be three, three and half , four feet of waterwhere it's docked at a small marina. And then in terms of the beach at Sand Point, the water had receded out probably a hundred feet in the shallows.

JJ: "Bruff says only minutes later things were pretty much back to normal. On Lake Superior, seiches are rare and difficult to predict. But by examining long term weather patterns, and observing changes in barometric pressure, the National Weather Service now issues regular shoreline water level forecasts for a few ports on Lake Erie and Lake Huron, where seiches are more common."

James Jones in an independent producer from Washington DC. The Weather Notebook is underwritten by Subaru with major support provided by the National Science Foundation.