It takes the right combination of wind,temperature,pressure and humidity to create even a weak tornado.

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For some races, the combination of water flowing west and wind blowing east creates a series of choppy five-foot waves.

WSJ: Before America's Cup Capsize, Concerns About Safety

Seven schools and one elderly day care centre have been closed because of a combination of problems caused by the wind and power cuts.

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The captain can also call on the assistance of an electronic positioning system that uses a combination of data from satellites, gyrocompasses, and wind and motion sensors to operate the thrusters automatically.

ECONOMIST: Marine technology: A voyage of discovery | The