ENSO & SST

ENSO and Sea Surface Temperatures

The equatorial Pacific Ocean is in a weak El Niño state, however the ocean and the atmosphere are yet to be fully coupled. The Southern Oscillation Index (SOI) has become more negative over the past month, with a 3-month (July-August) mean reaching -1.1, the first time it has been that low since the spring of 2002. Equatorial sea surface temperature (SST) anomalies are above normal across much of the equatorial Pacific: for August, the NINO3, NINO4, and NINO3.4 SST anomalies were +0.3°C, +0.9°C, and +0.6°C, respectively (3-month means +0.1°C, +0.8°C, +0.5°C).

Subsurface temperatures show a positive anomaly (exceeding +2.0°C) now centred near 110°W and propagating eastward. August averaged OLR anomalies show some anomalous convection about and west of the Date Line north of the Equator, and westerly zonal wind anomalies are evident across much of the Equatorial Pacific at present. The majority of available models indicate neutral conditions in spring 2004, most with above average SSTs in the NINO3.4 region. Slightly more than half indicate El Niño conditions during summer 2004/05, with a weakening, back to neutral conditions, into autumn 2005.

Sea surface temperature anomalies (°C) for August 2004

Mean sea surface temperatures (°C) for August 2004