Hurricane Watchers See Wild Season With No Relief From Pacific

(Bloomberg) -- U.S. forecasters see very little chance the hyperactive Atlantic hurricane season they’re expecting will be blunted by the Pacific’s power to roil world weather systems.

The odds the Pacific will stay neutral from August to October sit at 48%, the U.S. Climate Prediction Center said in its forecast Thursday. That means the water won’t affect the atmosphere by being too hot or too cold. The odds are 46% for a La Nina occurring, the result of cooler water which affects other global weather systems but won’t curb development of Atlantic hurricanes.

“The forecasters are more bullish on La Nina than the models,” said Michelle L’Heureux, a forecaster with the Climate Prediction Center. “We tend to tilt toward the possibility of La Nina, but we’re still not confident enough to issue a watch.”

A La Nina happens when the equatorial Pacific cools, touching off changes in the atmosphere that can alter weather patterns worldwide including the Atlantic. But it doesn’t produce the wind shear needed to shut down the Atlantic season.

What it does do generally is bring more rain to Indonesia and India, droughts to parts of Brazil and, if it stays strong through the remainder of the year, a dry, mild winter across the southern U.S.

The only thing that will bring on the wind shear needed to limit the Hurricane season is an El Nino, the weather pattern when the Pacific warms. Right now there is little chance that is going to happen.

U.S. forecasters expect 13 to 19 storms will form across the Atlantic this year, according to an outlook published in May. The average year produces 12. So far three storms have come out of the Atlantic with two hitting the U.S.

Meanwhile, if the Pacific stays neutral, that won’t make much difference for hurricanes coming west into Florida and the Gulf of Mexico, according to a paper by the Center for Ocean-Atmospheric Prediction Studies at Florida State University published in the American Meteorological Society’s Journal of Climate in 2007. It does, however, improve the chances the storms will miss the U.S. East Coast from Georgia to Maine.

Currently, the Pacific is showing slight signs of a La Nina. There has been an uptick in rain across Indonesia, as well as some cooler-than-normal ocean temperatures in key areas. None of those rise to the level needed for the U.S. to issue its La Nina watch, L’Heureux said.

Statistical models tend to favor the Pacific remaining neutral. But those models tend to be slow to pick up rapid oceanic changes, so that is why the human forecasters have split from their mathematical counterparts, L’Heureux said.

The outlook, as always, will become clearer with time. If the models start to favor odds about 50% then the U.S. will likely issue a La Nina watch for later this year. Across the Atlantic, however, it might not make much difference.

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