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Why Don't Hurricanes Hit L.A.?

By Andy BowersPosted Thursday, Sept. 18, 2003, at 2:59 PM ET

Listen to an audio version of this piece on NPR's Day to Day.

East Coast residents bracing for Hurricane Isabel today are old hands at fending off violent storms—an average of two make landfall each year. Why is the Eastern Seaboard consistently plagued by hurricanes, while the U.S. West Coast almost never suffers a direct hit?

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Two reasons, really. The first is that hurricanes form in the tropics, where (thanks to the Earth's rotation) winds tend to blow from east to west. That means tropical cyclones—including hurricanes—in the waters near the United States almost always move toward the west-northwest. So when they form in the Atlantic region, they head straight for the American mainland. But in the Pacific, they head farther out to sea. However, that path does take cyclones over Mexico and Hawaii from time to time. And of course, their westward movement also takes them toward land masses in Asia.

Related in Slate

Earlier this month, Explainer described how a tropical depression becomes a hurricane. And in 2001, Chatterbox's Timothy Noah investigated whether Hurricane Chantal was the first black hurricane.

The other reason hurricanes almost never hit California, Oregon, or Washington is that cyclones feed on warm sea water—preferably over 80 degrees. But the ocean temperature in the northern Pacific is usually under 75. In fact, there's no record of a tropical hurricane ever hitting the West Coast.

By the way, the words hurricane and typhoon both refer to the same thing—a severe tropical cyclone. The difference is that hurricane is used for storms in the northeastern Pacific, on the American side of the International Date Line, and typhoon is used on the western—or Asian—side.

Bonus Explainer: What's the origin of those interesting proper names given to hurricanes? Most people know that each hurricane season, tropical cyclones are named in alphabetical order to help scientists tell them apart. This year's storms in the Atlantic have ranged so far from Ana to Isabel. The practice began in earnest in the '40s and '50s with all female names. Male monikers were added in the late '70s. But according to the book Atlantic Hurricanes, it was an Australian forecaster in the early 20^th century who first used proper names for cyclones. The names he chose belonged to politicians he disliked.

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