The National Oceanic and Atmospheric Administration (NOAA) announced El Nino, a climate phenomenon with a significant influence on global weather and ocean conditions, has returned and will remain through the winter of 2009-2010.

The warming of central and eastern tropical Pacific waters usually occurs every two to five years, and lasts about 12 months. The last El Nino occurred in 2006.

El Nino can have both positive and negative effects on the weather. The positives include helping to suppress Atlantic hurricane activity. In the US, it brings beneficial winter precipitation to the Southwest, less wintry weather in the North, and reduced risks of wildfires in Florida.

Both California and the southern US can see El Nino's negative impacts of increased and harsh winter storms.

"Advanced climate science allows us to alert industries, governments and emergency managers about the weather conditions El Niño may bring so these can be factored into decision-making and ultimately protect life, property and the economy," says Jane Lubchenco, under secretary of commerce for oceans and atmosphere and NOAA administrator.

The National Oceanic and Atmospheric Administration (NOAA) announced El Nino, a climate phenomenon with a significant influence on global weather and ocean conditions, has returned and will remain through the winter of 2009-2010.