La Nina Near Peak, Will Linger for Several Months, U.S. Says

La Nina, a cooling of the Pacific Ocean blamed for record flooding in Australia, is near its peak and probably will last through the Northern Hemisphere’s spring, according to the U.S. Climate Prediction Center.

Measurements show most of the parts of the Pacific that are monitored were about 1.5 degrees Celsius (2.7 degrees Fahrenheit) below normal, the center in Camp Springs, Maryland, reported today in a statement.

“There remains considerable uncertainty as to whether La Nina will last into the Northern Hemisphere summer,” it said.

On average, La Nina occurs every three to five years and lasts nine to 12 months, with some persisting as long as two years. The phenomenon has been blamed for enhancing hurricane development in the Atlantic by limiting wind shear there that can tear budding storms apart.

Rain linked to La Nina has halted coal shipments and swamped cotton crops in Queensland state this month, after wet weather last year cut sugar output and downgraded east Australian wheat quality. La Nina has soaked rubber plantations in Southeast Asia, disrupted Indonesian tin output and brought dry conditions to corn and soybean areas in Argentina.

Its impact this year in the U.S. may include increased rain and snow for the Pacific Northwest, northern Rocky Mountains, Great Lakes and the Ohio Valley, according to the center. In addition, colder temperatures are possible in the Pacific Northwest and the North, excluding the New England states of Massachusetts, Connecticut, Rhode Island, Vermont, New Hampshire and Maine.

The threat of cool or neutral temperature conditions in the Pacific was part of the reason Colorado State University predicted the 2011 Atlantic hurricane season will probably be above-average.

An average hurricane season produces 11 storms, according to the National Hurricane Center in Miami. CSU researchers last month predicted 17 storms with winds of at least 39 miles per hour will form in the Atlantic after the season starts June 1.

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