NASA says new images from its Jason-2 oceanography satellite shows the tropical Pacific has switched from El Nino warm conditions to La Nina cool conditions.

"The central equatorial Pacific Ocean could stay colder than normal into summer and beyond," said oceanographer and climatologist Bill Patzert at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "That's because sea level is already about 4 inches below normal, creating a significant deficit of the heat stored in the upper ocean. The next few months will reveal if the current cooling trend will eventually evolve into a long-lasting La Nina situation."

Patzert said a La Nina is essentially the opposite of an El Nino and is associated with less atmospheric moisture, resulting in less rain along the coasts of North and South America. La Ninas also tend to increase the number of tropical storms in the Atlantic.

"For the American Southwest, La Ninas usually bring a dry winter, not good news for a region that has experienced normal rain and snowpack only once in the past five winters," Patzert said.

More information on El Nino, La Nina and Jason-2 is available at http://sealevel.jpl.nasa.gov.