El Niño/La Niña Update (December 2009) Document 01 December 2009 An El Niño event, which started in June 2009, is well established across the tropical Pacific. El Niño conditions are very likely to continue at least through the remainder of 2009 and into the first quarter of 2010. Some climate patterns typical of El Niño have been observed over the last several months. The expected continued presence of El Niño into early 2010 has implications for many climate patterns around the world over the next several months, keeping in view the fact that, in some regions, impacts typically continue during the decay phase. Decay of the El Niño event to near-neutral conditions across the tropical Pacific during the approximate March-May 2010 period is considered the most likely further development. The possibilities of a second year of El Niño conditions or rapid transition to a La Niña situation are considered unlikely at this time. Download document Share: Document type: El NIño / La Niña Update