SEA SURFACE TEMPERATURE (SST)

From mid-July through mid-August, SSTs were greater than 0.5ºC between 165ºE and 150ºW and also between 80ºW and 105ºW. By the end of September, the equatorial waters had sufficiently warmed to meet NOAA’s definition of El Nino. From mid-September to mid-October, equatorial ocean surface temperatures remained greater than 0.5ºC above average across the equatorial Pacific between 155ºE and the South American coast, with departures exceeding +1ºC between 165ºE and 145ºE and also between 85ºW and 125ºW. During this time, SST anomalies decreased in the western tropical Pacific and increased slightly in the eastern tropical Pacific. SST anomalies in mid-October remained positive (between +0.8ºC and +1.2ºC) in all of the Niño regions. In the subsurface waters there has been a gradual warming since February. During Aug-Sep 2006, positive subsurface anomalies were observed across most of the equatorial Pacific between 200 m depth and the surface.

Low-level easterlies have been weaker than normal over the western equatorial Pacific between 130ºE and 170ºE, and anomalous westerly winds have also dominated the east-central equatorial Pacific since July. Most statistical and coupled models predict slightly to moderately positive SST anomalies (weak to moderate El Niño) in the Niño 3.4 region through the next 3-6 months, consistent with the recent increase in SST and subsurface temperatures along the equator. With all these aforementioned factors in place, it seems likely that weak to moderate El Nino conditions will continue for at least the next 3 months.