ENSO Watch

Changes are not significant...

2009-09-28 13:30 UTC / 21:30 HKT

Similar to August, sea surface temperatures in the equatorial Pacific has not changed much in September. SST departures are about 1.0 degree Celsius from 160E to 110W. At a depth of about 150 m, positive anomalies of 2 degrees Celsius can be observed near the Dateline.

Unlike an ordinary El Niño event, the equatorial western Pacific and Indian Ocean are also warmer than average. 30-day average Southern Oscillation Index is slowly increasing (positive 4.32 today). July-to-Aug's Multivariate ENSO Index was positive 0.978.

SSTs should go on increasing in the coming few months. El Niño conditions will continue through winter. Yet, latest forecast suggests that the positive anomaly of Niño 3.4 may not be as large as previously predicted.

The next update is scheduled for late October.

Jams

What is ENSO? El Niño and La Niña?

ENSO stands for El Niño-Southern Oscillation. It's the see-saw in atmospheric pressure between the Eastern Pacific Ocean and the Eastern Indian Ocean. It was found that the pressure oscillations can be related to sea temperatures over the equatorial Pacific.

El Niño refers to the unusual warming in the equatorial Eastern Pacific.
La Niña is the opposite of El Niño. During La Niña years, the equatorial Eastern Pacific is cooler than normal.

Both El Niño and La Niña have impacts on climate conditions over the World.

There are interactions between the ocean and the atmosphere (sea-air coupling). The Southern Oscillation Index (SOI) is used as a tool to monitor the ENSO status.

More information on SOI can be found in http://www.longpaddock.qld.gov.au/.