El Niño Status and Forecast

The La Niña event continues to reign across the equatorial Pacific Ocean but recently has shown signs of weakening. Sea surface temperatures (SSTs) this past week were still quite cool across the eastern Pacific, measuring 1.2 degrees Celsius (about 2 degrees Fahrenheit) below average but have slightly warmed since the end of January. The NOAA-Climate Prediction Center (CPC) also noted that the far eastern Pacific SSTs had warmed to near-average levels, and subsurface water temperatures also had warmed slightly. The weakening event is also evident in the atmosphere. Easterly winds at the surface along the equator are currently with less strength than in previous months. However, the atmosphere is still fully engaged and responding to the current La Niña event, which is evident in the strongly positive Southern Oscillation Index (SOI, Figure 13a).

Forecasts produced by the International Research Institute for Climate and Society (IRI) continue to indicate a high probability (greater than 90 percent) that La Niña conditions will continue into the early spring (Figure 13b). The chance of La Niña conditions persisting into the April–June period falls to 49 percent, while the chance of neutral conditions returning rises to 42 percent. IRI notes that late winter is the typical time for La Niña events to weaken, and that is reflected in forecasts for the remainder of the spring. However, this is the time of year when the El Niño Southern Oscillation (ENSO) forecast confidence is lowest, according to the CPC, so it is unclear whether neutral conditions will rapidly return later this spring or La Niña conditions will continue to linger. Some models suggest a high chance that La Niña will persist for another year.

The continuation of La Niña conditions in the short-term will continue to have profound impacts on the Southwest, likely delivering below-average precipitation to Arizona and New Mexico.