El Niño Status and Forecast

A La Niña Advisory remains in effect this month as the current La Niña event continues to gain strength. The NOAA–Climate Prediction Center (CPC) issues La Niña Advisories when conditions are observed and expected to continue.

Sea surface temperatures (SSTs) in the central and eastern Pacific Ocean continue to cool. The most recent weekly measurements indicate that SSTs in the key Niño 3.4 region in the central Pacific Ocean are -1.5 degrees Celsius, indicating a moderate to strong La Niña event; this is somewhat colder than the -1.20 degrees C temperatures observed in August. The Southern Oscillation Index (SOI) remained high again this month, indicating a strong atmospheric response to the below-average SSTs (Figure 12a). Stronger-than-average easterly winds along the equator in the eastern Pacific are helping to elevate cooler-than-average water to the surface, further reinforcing the strong easterly winds wafting across the Pacific. This self-reinforcing cycle between the ocean and atmosphere is expected to help maintain and potentially strengthen the La Niña event through the upcoming fall and winter seasons.

Forecasts issued by the International Research Institute for Climate and Society (IRI) continue to show a high probability that La Niña conditions will persist through at least the winter season (Figure 12b). The chance of the current La Niña event continuing through the January–March period is 90 percent; in contrast, the return of an El Niño event is only 1 percent. The strong indication for a winter La Niña has implications for weather in the Southwest. Seasonal forecasts issued by the CPC indicate increased chances for drier-than-average conditions across all of Arizona and New Mexico through May.