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Boston Weather: 38.0°F | A Few Clouds and Windy
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Who’s Eddy?

Many people are often foiled by the assumption that today’s weather will be the same as yesterday’s weather, finding themselves wearing shorts when things suddenly take a turn for the cooler side. Such quickly changing weather is a consequence of living in the midlatitudes, where the circulation pattern is dominated by what meteorologists call eddies.

An example of eddies are the swirling patterns in a fast moving stream as water flows around obstacles. In a meteorological sense, eddies can be of different scales. The high and low pressure systems drawn on the weather map are examples of synoptic eddies. This type of eddy occurs on large scales of about a thousand kilometers or several states wide. They move generally from west to east and cause our weather pattern to change every few days. A weather map in the tropics, however, would not have any highs or lows drawn on it. Another type of eddies, mesoscale eddies, occur on smaller scales of around a hundred kilometers, perhaps due to large features in the landscape such as mountains. Even smaller turbulent eddies occur near the surface, as air flows over and around things on the ground.

Sunny but much cooler weather visits us today and tomorrow, with rain likely on Sunday.

Extended Forecast

Today: Sunny and much cooler. High 65°F (18°C). North winds 15 to 20 mph.

Tonight: Clear and chilly. Low 45°F (7°C).

Tomorrow: Mostly sunny. High 63°F (17°C). Southeast winds around 10 mph.

Sunday: Rain. High 66°F (19°C)