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Why do most storms in North America move from west to east, but hurricanes move east to west?

Dear Cecil:

With the recent deluge of hurricanes and tropical storms in the Atlantic, I couldn't help but wonder. Why do most weather systems move from west to east over North America, but hurricanes and tropical storms in the Atlantic move from east to west?

Ed in Massachusetts

Cecil replies:

Dear Ed:

Because they start in the tropics, you silly goose, where the prevailing winds, AKA the trade winds, are out of the east. Lucky for Columbus and a million other mariners in the age of sail. Maybe not so lucky for you.

The basic flow of winds in the North Atlantic in hurricane season is clockwise. The center of this circular flow is something known as the "Bermuda high," which in the summer months typically parks itself in the mid-Atlantic somewhere between 30 and 35 degrees north latitude.

For complex geophysical reasons having to do with the rotation of the earth, the tropical winds in the hurricane-spawning region south of the Bermuda high basically blow west. Once a hurricane gets up to speed, it may continue due west, across Central America, and out to the Pacific.

More commonly, it may circle around the Bermuda high, first northwest and then north. Later, after having leveled or at least threatened various points of interest on the eastern seaboard, the hurricane or what’s left of it heels over to the northeast and east and back out to sea.

So that’s why the East Coast regularly gets pasted by hurricanes–the weather systems are set up like an automatic pitching machine to lob those babies in there. Where exactly the next fastball is going to come in nobody knows. But the strike zone, generally speaking, is you.

Cecil Adams

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