El Niño/La Niña Southern Oscillation (ENSO)
La Niña conditions in the tropical Pacific have persisted and strengthened as trade winds intensified during mid-July to mid-August 2022. It is likely that these conditions will continue at least for the remainder of 2022, becoming the first “triple-dip” La Niña event of the 21st century. WMO Global Producing Centres of Long-Range Forecasts predict the continuation of the current La Niña over the next six months, with a 70% chance in September-November 2022 but gradually decreasing to 55% in December-February 2022/2023. The probability for the return to El Niño–Southern Oscillation (ENSO) neutral conditions is estimated to be around 30 to 40%, for the same periods, respectively. The chance of El Niño developing is near-zero in September-November increasing to very low (around 5%) towards the end of forecast period (December-February 2022/2023). National Meteorological and Hydrological Services (NMHSs) will closely monitor changes in the state of ENSO over the coming months and provide updated outlooks, as needed.
The equatorial Pacific Ocean is still experiencing La Niña conditions (as of mid-August 2022). The sea surface temperatures ranged from -0.8 to -1.2 degrees Celsius (for the week centered on 17 August 2022), with below-average subsurface temperatures in the central-eastern Pacific sustaining the cooler sea surface temperatures. The overlying atmospheric conditions, including surface and upper-level winds and patterns of cloudiness and rainfall, remain consistent with La Niña. The Southern Oscillation Index (SOI: defined by the standardized Tahiti minus Darwin sea-level pressure difference) showed a sharp decline in early July 2022 but has remained above the threshold of La Niña and has even slightly picked up again since the beginning of August 2022. Anomalously dry conditions have been observed in the central Pacific (west of International Date Line), with enhanced convection and precipitation over Indonesia and the western Pacific. On the whole, observed oceanic as well as atmospheric conditions indicate a continuation of the current La Niña event.
Using the recent observations as the starting point for their dynamical seasonal prediction systems, the WMO Global Producing Centres of Long-Range Forecasts routinely issue global-scale climate forecasts for the coming months. Their latest forecasts and expert assessment indicate that there is a moderate probability for the sea surface temperature anomalies in the central and eastern equatorial Pacific to remain between -0.5 and -1.0 degree Celsius during next three overlapping seasons (September-November, October-December, and November-January). The likelihood of a continuation of the current La Niña is forecasted to be about 70% for September-November, but to decrease slightly to about 55% during December-February 2022-23. The probability for ENSO-neutral conditions during next six months is estimated to range from 30%, in September‑November, to 40%, in December-February, and the chance of El Niño developing is near-zero to very low (around 5%) for the same periods, respectively. It is likely that the La Niña will persist through boreal winter 2022-23, making it the first “triple-dip” La Niña event spanning three consecutive years of the 21st century, and only the third since 1950.
It is important to note that El Niño and La Niña are not the only factors that drive global and regional climate patterns, and further that the magnitudes of ENSO indicators do not directly correspond to the magnitudes of their effects. At the regional level, seasonal outlooks need to assess the relative effects of both the ENSO state and other locally relevant climate drivers. Regionally and locally applicable information is made available via regional and national seasonal climate outlooks, such as those produced by WMO Regional Climate Centres (RCCs), Regional Climate Outlook Forums (RCOFs) and National Meteorological and Hydrological Services (NMHSs).