Pacific ENSO Update

4th Quarter, 2007 Vol. 13 No. 4

SEA SURFACE TEMPERATURE (SST)

Sea surface temperatures (SST) in the equatorial eastern Pacific have been cooler than average since January 2007. Over the past several months, below average SSTs have expanded westward, and negative anomalies now extend from the Date Line to the west coast of South America. By mid-October, equatorial Pacific SSTs were more than -0.5ºC below average east of 170°E, and more than -1ºC below average between 160ºW and the South American coast. SSTs were more than +0.5ºC above average in much of the western Pacific. During August – September 2007 equatorial sub-surface temperatures were generally below average in the region east of the Date Line, while positive temperature departures were confined to the western Pacific. The most recent period shows negative anomalies between the surface and 150 m depth across the central and eastern half of the equatorial Pacific Ocean, with the largest departures between 120°W and 90°W. Current equatorial Pacific SST trends indicate La Niña conditions will likely strengthen during the next several months.