Our second La Nina year in a row is in full swing now, and is forecast to last through the winter. In November, the average surface water temperature in the Nino3.4 region of the central Pacific Ocean was about 1.0°C cooler than the long-term average. A “double-dip” La Nina is not uncommon—seven La Nina winters in the 1950-present historical record followed La Nina the previous winter: 1955, 1971, 1974, 1984, 1999, 2008, and 2011. In fact, two years, 1975 and 2000, were third-year La Ninas. Only four years, 1964, 1988, 1995, and 2005, were single-year La Ninas.

La Nina is expected to affect global weather patterns this winter. As I mentioned above, the stronger Walker Circulation means there is more convection (rising air, clouds, and storms) over Indonesia and the far western Pacific, and even less than average over the central Pacific.


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LaNina


1979-2018