July 2, 2009

New El Nino Information Emerges

Scientists are now saying that El Nino may have two personalities.

They've known for a long time that the warming of the tropical Pacific Ocean affects weather around the world. However, researchers now say it may come in two forms with different impacts.

A new study suggests that El Niño may be causing not only a greater number of hurricanes than in average years, but also a greater chance of hurricanes making landfall.

Climatologists at the Georgia Institute of Technology published the study that appears in the July 3, 2009 edition of the journal Science.

"Normally, El Niño results in diminished hurricanes in the Atlantic, but this new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall," said Peter Webster, professor at Georgia Tech's School of Earth and Atmospheric Sciences.

Researchers say the traditional El Nino tends to reduce the number of Atlantic hurricanes.

But a form the Georgia Tech scientists call El Nino Modoki can lead to more hurricanes than usual in the Atlantic Ocean.

Modoki, from Japanese, refers to something that is "similar but different."

The traditional El Nino involves a periodic warming of the water in the eastern part of the tropical Pacific. Peruvian fishermen named it after the baby Jesus because it tended to first appear around Christmastime.

Compare that to El Nino Modoki, where the warming occurs farther to the west, in the central Pacific.

It's not clear why this new form is occurring, said Webster, who co-authored the report.

"It may be responding to some (climate) oscillation or it may be in response to global warming," Webster said.

Atmospheric scientists can better forecast weather, including the number of Atlantic hurricanes thanks to a better understanding of El Nino and its cold-water counterpart La Nina.

Study co-author Judith A. Curry said she feels that "there is about a 50 percent chance that we could have one of the Modoki years emerging by late summer."

"We'll have to see how it plays out, but we could be seeing increased (hurricane) activity," Curry, chair of atmospheric sciences at Georgia Tech, said in a telephone interview.

Greg J. Holland of the National Center for Atmospheric Research likes the finding, saying the study "has important consequences for the predictability of global weather patterns."

Hurricane prediction could be improved by breaking El Nino into two modes, eastern Pacific warming and central Pacific warming.

The National Weather Service predicts nine to 14 named tropical storms this year, of which four to seven are likely to be hurricanes.

Those future storms have a major impact on the United States. Commerce Secretary Gary Locke has pointed out that "more than 35 million Americans live in regions most threatened by Atlantic hurricanes."


Image Caption 1: The 2008 hurricane season was one of the most active on record. In this image, taken on August 28, 2008, three storms can be seen in various stages: Fay, Gustav and Hannah. Credit: National Oceanic and Atmospheric Administration


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