El Niño Status and Forecast

The La Niña event that drove record dry conditions across parts of southeast Arizona and much of New Mexico this past winter has officially come to an end. The NOAA–Climate Prediction Center (NOAA–CPC) reports that sea surface temperatures (SSTs) have warmed to near-average levels across much of the eastern Pacific Ocean and are indicative of a return to ENSO-neutral conditions. The International Research Institute for Climate and Society (IRI) also notes that the Southern Oscillation Index (SOI) rapidly shifted from near-record levels in April to near-average values as of mid-May in concert with the warming SSTs (Figure 15a). The shift in the SOI indicates the atmosphere is rapidly adjusting back to an ENSO-neutral circulation pattern and that the lagging effects and impacts of the recent La Niña event may be short-lived.

IRI notes this is a particularly difficult time of year to develop longer-range ENSO forecasts, but short-term forecasts consistently point toward the persistence of ENSO-neutral conditions through at least the summer. IRI forecasts predict a 57 percent chance that neutral conditions will continue through the June–August period, with a 22 percent chance that La Niña conditions will return and a 21 percent that an El Niño event will develop (Figure 15b). These forecast probabilities remain relatively constant through next fall and winter. Some models have hinted at the possibility of a weak El Niño developing later this summer or fall, but forecast confidence is very low. ENSO-neutral conditions provide very little forecast guidance through the summer season in Arizona and New Mexico; this is reflected in the equal chances July–September precipitation outlook recently posted by NOAA–CPC
(see Figures 11a–d).