It was only June when there were expectations of an El Nino coming. But the sea has cooled rapidly since then — much faster than usual — and now NOAA thinks a La Nina is slightly more likely. If so, global temperatures will decline.
Cold water is upwelling across the Eastern Pacific. Sea Surface Temp Anomaly. | Image Sept 6, 2017
I notice that there is also unusually cold water on the surface of the eastern Indian Ocean near West Australia (see below). One spot is 2.5C cooler than normal. I don’t know the significance…
Cooling ocean in the east Indian Ocean too. Sea Surface Temp Anomaly. | Image Sept 6, 2017
It may be a milder wetter summer downunder (our grid managers will be happy about that.) In the US, drying conditions in the south, but more snow or rain in the midwest, Northern California. A cooler snowier winter in Canada. It means more Atlantic Hurricanes.
The best explanation I’ve heard on how El Nino works is from Bill Kininmonth: The deep oceans drive the atmosphere.