NOAA Makes It Official: La Nina Has Arrived

See here (PDF). Top bullet points:

•La Niña conditions are present across the tropical Pacific. •SST anomalies have become more negative in the central equatorial Pacific, and remain positive in the western equatorial Pacific. •Most dynamical models predict a further strengthening of La Niña in the next couple of months, while half of the statistical models indicate a weak La Niña through the end of the year. •Recent equatorial Pacific SST trends and model forecasts indicate La Niña conditions will develop further during the next several months.

I'll have more shortly on what this means for the rest of the Atlantic hurricane season.