El Niño Status and Forecast

Sea surface temperatures (SSTs) are near average across much of the eastern equatorial Pacific Ocean and ENSO-neutral conditions are returning after the rapid retreat of La Niña in early May. The Southern Oscillation Index (SOI) values have also dropped toward near-average levels, which is additional evidence that neutral conditions are gaining a stronghold in the Pacific Ocean (Figure 13a). The NOAA-Climate Prediction Center (CPC) notes, however, that remnants of the recent La Niña event, albeit weak, are still persisting in the atmospheric circulation patterns, including slightly enhanced easterly winds along the equator. These conditions are expected to continue to weaken through June as the atmosphere catches up with the SSTs.

Forecasts issued by the International Research Institute for Climate and Society (IRI) show a high probability that neutral conditions will continue through the summer and well into next fall and winter. The chance of neutral conditions persisting is at least 70 percent for all time periods through next December, while El Niño and La Niña have a 15 percent chance of occurring (Figure 13b). IRI notes that some warmer-than-average subsurface water has emerged across the eastern Pacific, raising the prospect of an El Niño event developing, but forecast models do not support this development yet. Both CPC and IRI project neutral conditions through the rest of 2011. The lack of a strong ENSO signal does not clarify monsoon forecasts, which currently have equal chances of above-, below-, and average-precipitation for the monsoon season.