La Niña's Return May Mean More Storms

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Here's something hurricane-weary residents of Florida and the rest of the southeast didn't want to hear: La Niña is back.

Government forecasters on Thursday announced ''the official return of La Niña,'' making it sound more like a rock music tour than a weather phenomenon that can enhance the development and strength of hurricanes.

La Niña is the periodic cooling of the eastern Pacific Ocean, and it tends to occur every three to five years.

Sea temperatures even one degree Fahrenheit below normal can inhibit the development of crosswinds that can reach into the Atlantic and weaken or tear apart hurricanes. In the absence of those crosswinds, more hurricanes can form and strengthen.

Experts cautioned that they cannot yet draw meaningful conclusions from the return of La Niña, which was described as moderate, but no one in the hurricane zone needs this.

''Seeing La Niña now certainly isn't good news,'' said Chris Landsea, science officer at the National Hurricane Center in west Miami-Dade. He and other experts said the phenomenon was slowly strengthening but could dissipate by summer when it matters most.

''Everyone wants to know what's going to happen this coming season, given the horrible impacts of the last two years,'' Landsea said. “We would love to know now how many there will be and where they will go and we can't say that with much certainty.''
Still, this much is known.

''If there's a La Niña around during hurricane season, the odds for more frequent and stronger hurricanes go up,'' said Ed O'Lenic, an expert at the National Oceanic and Atmospheric Administration's Climate Prediction Center.

He noted more intense interest in the subject this year, which he called “understandable and appropriate, given what's at stake.”

Other effects associated with La Niña include drought in parts of the South and Southwest and above-average rain in the Northwest and the Tennessee Valley.

La Niña is the opposite of El Niño, a warming of the eastern Pacific that can suppress hurricane development because it generates more crosswinds. The last La Niña appeared in 2000-2001.

In December, a team led by private hurricane forecaster William Gray of Colorado State University predicted 17 named tropical storms in 2006 that grow into nine hurricanes.

That forecast accounted for a minimal La Niña and called for an above-average storm formation, but the forecast suggested less activity than during the record-setting 2005 season, when 27 named storms developed into 15 hurricanes.

The six-month hurricane season begins June 1.