El Niño Status and Forecast

La Niña conditions weakened substantially during the past 30 days and the NOAA-Climate Prediction Center (CPC) states that March will probably be the last month with an active La Niña Advisory, as ENSO-neutral conditions are expected to return by the end of April.

During the last couple of months, a pool of cold water below the sea surface has been critical in supporting the La Niña. This below-surface water has substantially warmed in the eastern Pacific over the past 30 days and, in combination with rising sea surface temperatures (SSTs), indicate  the days are numbered for the La Niña event. Ocean water is usually the leading indicator of changes in ENSO conditions and it will take the atmosphere several months to catch up. Current atmospheric circulation patterns remain very La Niña-like, with enhanced easterly winds and suppressed convection in the central Pacific. Consequently, the Southern Oscillation Index (SOI) remains positive (Figure 13a). This pattern should yield to typical atmospheric circulation patterns by the late spring and summer.

Official forecasts issued jointly by NOAA-CPC and the International Research Institute for Climate and Society (IRI) indicate greater than a 70 percent chance that ENSO-neutral conditions will develop in the April–June period (Figure 13b). Forecasts also indicate that ENSO-neutral conditions will likely persist through the upcoming summer and fall seasons. The chance of an El Niño event returning also rises by late summer, but confidence is low in the forecast. However, since 1900 there have been 10 two-year La Niña events. In four of these events, La Niña endured for a third consecutive winter, while El Niño developed in the other six winters.