These recent La Ninas have…
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These recent La Ninas have been remarkable for their persistence, but I would not say that the magnitude of the cold water currently in the tropical Pacific is particularly remarkable - the September Nino 3.4 index was the 7th lowest since 1950, so it is a healthy La Nina but currently not one of the strongest. You can get more information on the current state of the Pacific in the context of recent observations at this site.
In terms of the long-term trend, the oceans have been warming up consistently overall, but the eastern tropical Pacific (the main ENSO region) has not. This is a bit of a puzzle for climate scientists, and an important one. Look out for a post on this topic on the ENSO Blog sometime in the coming months.