El Niño In Focus

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El Niño, a warming of equatorial waters in the Pacific Ocean that wreaks havoc with world weather conditions, has formed and will last into 2007, the National Oceanic and Atmospheric Administration reported. The good news: El Niño has already helped make the Atlantic hurricane season milder than expected, said a NOAA forecaster.

What is El Niño?

El Niño is a warming of the Pacific Ocean centered directly on the equator between South America and the International Date Line. It typically extends several degrees of latitude to either side of the equator.

How Does El Niño Affect The Weather?

It has important consequences for weather and climate around the globe.

For people who live in Indonesia, Australia or southeastern Africa, El Niño can mean severe droughts and deadly forest fires. Ecuadorians, Peruvians, or Californians, on the other hand, associate it with lashing rainstorms that can trigger devastating floods and mudslides.

For an interactive look at El Niño, click here.

Severe El Niño events have resulted in a few thousand deaths worldwide, left thousands of people homeless, and caused billions of dollars in damage. Yet residents on the northeastern seaboard of the United States can credit El Niño with milder-than-normal winters (and lower heating bills) and relatively benign hurricane seasons.

Why Is It Called "El Niño?"

El Niño means "The Little One' in Spanish. El Niños originally were recognized by fisherman off the coast of South America as the appearance of unusually warm water in the Pacific Ocean, occurring near the beginning of the year. This name was used for the tendency of the phenomenon to arrive around Christmas.

Can meteorologists predict El Niño?

According to NOAA, once an El Niño has started, meteorologists can predict reasonably well its subsequent evolution over the next 6 to 9 months. But before it has started, we have very little skill in predicting the onset before the event has become obvious. There are a variety of theories for why El Niños start, but none of them has given us real skill in making a forecast in advance, the way we can for thunderstorms.

Why does El Niño occur?

El Niño results from interaction between the surface layers of the ocean and the overlying atmosphere in the tropical Pacific. The physical processes are complicated, but they involve unstable air-sea interaction and planetary-scale oceanic waves.

For More El Niño Resources:

• For a useful explanation of El Niño, click here for NOAA's explanation.

National Academy of Sciences El Niño Web site

• The Climate Analysis Center at the U.S. National Center for Environmental Prediction provides up to date Reginal Climate Monitoring information from many parts of the world.