El Nino Returns

Sept. 13, 2006 — -- El Nino is back.

Forecasters say a new El Nino -- a patch of unusually warm water in the tropical Pacific Ocean that develops every few years -- will mean warmer temperatures and stormier weather for the United States this winter.

In past years, El Ninos have been blamed for rearranging world weather patterns. Typically, they bring increased storms to the West Coast, and wet weather to the Southeast.

The good news is that El Nino may help explain why the 2006 Atlantic hurricane season has been relatively quiet.

Last year's season set a record of 27 named tropical storms and hurricanes. This year, there's been only seven.

"El Nino alters the atmospheric circulation pattern," said Vernon Kousky, an El Nino expert at the National Oceanic and Atmospheric Administration. "There is an increase of winds that shear off the tops of thunderstorms before they have a chance to spin up and become a tropical storm. Wind shear is a bad thing for hurricanes."

Kousky doesn't want anyone to get complacent.

"We don't want people to let their guard down," he said. "There's still a lot of hurricane season left to go, and you can still have substantial hurricane activity."

This year's El Nino began in late August or early September, later than the usual spring start.

That means the effects will be more moderate than the strong El Nino season of 1997-1998, for example.

Kousky says this El Nino event will likely hang around until early spring.

When an El Nino forms in the Pacific, it generally means drier conditions for places like Malaysia, Indonesia, and the Philippines, researchers say.

As winter approaches, El Nino will begin to change the jet stream over the Northern Hemisphere and affect the temperature and weather patterns over the United States.

The northern United States, much of the West, Great Lakes, and parts of New England will experience warmer than normal temperatures.

"And we'd expect stormier, wetter conditions for much of the Southwest, southern Texas, Florida and the Southeast," Kousky said.

Some scientific studies have suggested that El Nino events could become much more common in the future if the amount of heat-trapping greenhouse gasses in the atmosphere continues to increase.

A team of scientists published a study Monday that linked warming ocean temperatures to human-caused greenhouse gas pollution, for example.

Not all scientists agree that global warming will affect El Nino conditions, but Kousky says researchers are studying the issue.

"El Nino is a natural phenomenon that transports heat out of the Tropics and gives it away so we maintain some kind of climatic equilibrium," Kousky said.

"If we alter the normal temperature distribution due to global warming, the whole globe will warm up. Maybe the new climate state will not require an El Nino. Another possibility is that we could go into a perpetual El Nino."

El Nino means little boy in Spanish and refers to the birth of Jesus, because the effects of the weather pattern usually reach a peak around Christmas.