Monday, June 14, 2010

ENSO 3.4 reaches La Nina threshold

According to the newest
weekly report about El Nino and La Nina conditions (PDF, HTML),
the sea surface temperature anomaly in the Nino 3.4 region reached minus 0.5 °C (see page 5 of 30) which is the threshold defining a La Nina.

However, similar or colder average temperatures have to exist in the equatorial Pacific for five consecutive overlapping three-month periods for the La Nina-like conditions to be declared a La Nina episode.

Although models are split, I think it is more likely than not that the conditions will actually become a La Nina episode. Note that the last complete 3-month period (MAM 2010) was still safely in the El Nino range, +0.8 °C!

The expected cooling may help to keep the average 2010 temperatures below those of 1998.

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