Ill Wind from Hawaii

The forecaster at the San Francisco airport was busily recording weather data from ships and planes out in the Pacific. And as the hieroglyphics of his profession spread across his maps, he recognized signs of trouble. The Pacific High, a mass of high-pressure air that normally occupies most of the area between Alaska and Hawaii, shielding California in winter from rain-bearing oceanic winds, was breaking in two before his eyes. Half of it had moved southward to the latitude of Mexico while the other half had shifted north ward to the Gulf of Alaska. Through the low-pressure gap that resulted, a stream of warm, moist, tropical air, 500 miles wide and dotted with storms, was flowing toward Northern California.

The forecaster wasted no time issuing a warning, and trouble came right on schedule. For ten days last month a wind from Hawaii blew across the Northern California coast, dropping its moisture when forced to climb over the mountains. Heavy rain fell, in some places 35 inches. Eastward all the way to Idaho, the high mountains got the worst drenching; the warm rain melted accumulated snow, adding another ten inches to the foaming runoff. Before the ill wind from Hawaii stopped blowing, it had started disastrous floods that cost nearly 50 lives and almost a billion dollars in damage.

Canadian High. While the Pacific Northwest was suffering, the rest of the U.S. was enjoying unusually calm and warm winter weather. The Canadian High, another meteorological fixture, moved southward to cover the central part of the continent, protecting it from arctic cold and keeping the bad weather of the Pacific from penetrating much beyond the Rocky Mountains.

After ten days, the Pacific High pulled itself together again. The normal pattern of northwest winter weather brought cold air from Alaska. Snowfall put ski resorts back in business again. The steep rivers stopped foaming, and river towns began cleaning up the debris left by floods. Then, early last week, the sheltering Pacific High broke in two once more, and another wind from Hawaii headed for California. Another warning went out, and inhabitants of flood-damaged towns headed for the hills.

Warm Water or Jet Stream. But by week's end the Pacific High was knitting itself together again and West Coast weathermen were trying to spot the original cause of the trouble. Some of them blamed the jet stream, the belt of high-altitude wind that blows around the planet in mid-latitudes. It has been unusually swift this winter, reaching speeds of 150 m.p.h., and has crossed the U.S. in an unusual pattern, curving down from western Alaska to Southern California and then slanting up to Chicago. It may have had some influence on low-altitude weather, but experts do not agree. One group blames the West Coast's time of weather trouble on a great patch of unusually warm surface water far out in the Pacific, which may have somehow encouraged the Hawaiian wind. Most meteorologists ruefully admit that they cannot spot the ultimate cause of the trouble with any assurance. "If we could tell what makes the Pacific High come apart," said one, "we could solve most of the mysteries of long-range weather forecasting."

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