Last year, El Niño was fast approaching. Now it began to dwindle, and the next question is: what's next? El Niño, neutral or La Niña? A persistence of El Niño seems most unlikely; forecasts favor La Niña (65%) or neutral for the end of 2024. Once set, La Niña should probably (85%) stay until next  Northern Hemisphere winter. 

Both phenomena have been monitored using satellites, either in situ buoy network (TAO array) which data are retrieved using satellites, or altimetry and SST satellites directly measuring the ocean properties. Buoys enable to measure in-depth, while satellites have the broader Pacific view. Both are complementing each other to try and understand better this complex ocean-atmosphere oscillation. We still have a lot to discover about it, and each satellite-monitored strong El Niño has shown a new facet of this phase - stopping its development in the middle of the Pacific, or not being as strong as forecasted (but still being rightly forecasted). Forecasts are getting better and better from this understanding, to help and mitigate the impacts on the regions where the ENSO-born anomalies are hitting the hardest. 

Continuity in the time series, and the large altimetry constellation currently in flight, are helping in these improvements, and in the forecasting. Sentinel-6B, Sentinel-3C&D will take over the monitoring in the coming years - waiting for the next generation of altimetry satellites.