BACKGROUND: NASA satellite data indicates El Niño has returned to the tropical Pacific Ocean, noting a general warming of ocean temperatures and a rise in sea surface heights in the central and eastern Pacific along the equator. These are indicators of a developing El Niño. However, it is relatively weak and may not persist, since it is much less intense than the last major El Niño episode in 1997-1998. If the ocean waters continue to warm and spread eastward, the effect will strengthen, perhaps brining much-needed rainfall to the southwestern and southeastern United States this winter.
ABOUT EL NINO: El Niño is a cyclical warming of the ocean waters in the central and eastern tropical Pacific that generally occurs every three to seven years, usually around the holidays. It is associated with changes in air pressure and the movement of high-level winds, and can affect weather worldwide. In the United States, En Niño normally results in warmer-than-normal temperatures across the northern and western states. Wetter conditions result in the south, with dry weather across the Ohio Valley and Pacific Northwest. El Niño typically peaks during the winter months. It alternates with La Niña, the cooling of ocean waters in the same region of the Pacific.
IS IT RELATED TO GLOBAL WARMING? Scientists, don't discount the possibility, but there is very little information available linking El Niño to global warming. That's because little is known about the cause of El Niño, although scientists do have a good understanding of how the effect evolves once it begins. El Niños in different years can vary greatly in strength, indicating it is very sensitive to large-scale climate change. But we won't have a statistically significant sampling of such events for at least another 100 years
The American Meteorological Society contributed to the information contained in the TV portion of this report.