The Niño indices have turned. Nino3.4 and the Southern Oscillation Index (SOI) have been in the El Niño phase for almost 2 years but they have both just moved weakly into the La Niña phase and everyone is waiting to see what the future holds.
During La Niña the trade winds are stronger than usual, allowing a warm pool of water to pile up north of New Guinea, and altimeter data is showing us that the sea level is starting to rise (right). Sea level anomalies north of New Guinea (SLA-NNG) are strongly negatively correlated with Nino3.4 and both indices have recently jumped sharply. [more]