ENSO neutral conditions are expected to continue over the next several weeks, but La Niña is slightly favoured over ENSO neutral during September-November.
From mid-August into early September, a surge in tropical Pacific trade winds will nudge the ocean in a La Niña-like direction. An alternative measure of central Pacific SSTs, called the relative oceanic Niño Index, has had an average anomaly of -0.6˚C over the last month and is more aligned with La Niña-like oceanic conditions.
As of 20 August, the traditional 30-day Niño 1+2 Index anomaly was -0.45˚C, within the neutral range. The 30-day NINO3.4 Index anomaly (in the central equatorial Pacific) was 0.0˚C.
The Southern Oscillation Index (SOI) was in the neutral range during June-August (-0.2), while the August value was +0.4 (in the neutral range).
The subsurface equatorial Pacific continues to be 4˚C to 6˚C cooler than average just below the surface in the east of
the basin.
Above average oceanic temperatures persist in the central and western parts of the basin, with much cooler temperatures in the east. The West Pacific Warm Pool is becoming more unusually warm, which is also reflective of the potential development of La Niña.
The South Pacific Convergence Zone was very close to its climatological normal position during August.
During September-October, model guidance favours an enhancement in convective forcing over the western Pacific and Maritime Continent, consistent with a developing La Niña. This may lead to enhanced rainfall for some countries such as Palau, Papua New Guinea, and the Solomon Islands (based on the decile precipitation forecast for September and September-November; see pages 6-7 for more information).
