What steers hurricanes?

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Dear Tom,
In some years hurricanes tend to hit the U.S. Gulf or Atlantic coasts, but in other years they turn northeast and move out to sea. Why the difference?
— Mary King, Lisle
Dear Mary,
Hurricanes are steered by the upper wind flow. Since most of the storms form in the deep tropics, they tend to move west with the prevailing easterly wind circulation. As these storms continue west, their movement begins to be influenced by the clockwise wind circulation around the semi-permanent Bermuda high pressure system.
When that high extends farther west, the storms tend to travel into the Caribbean and Gulf of Mexico, and often turn north, threatening the Eastern Seaboard. When the Bermuda high is positioned farther east, the tropical cyclones tend to recurve to the north and northeast, traveling away from the U.S. mainland.

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