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03 November 2011

Satellite images shows La Nina is back

Image: NOAA (Click on image for larger view.)

A sea surface anomaly, or departure from the average temperature, is calculated by subtracting the temperatures from a time period of interest from the 30-year average (1981-2010) for the same time period. The resulting data shows areas that are hotter or colder than normal.  The world has been in a La Niña, or at least a colder anomaly period, since spring of 2010. The expectations now are that this weather pattern will continue until the spring or summer of 2012.

La Niña is a coupled ocean-atmosphere phenomenon that is the counterpart of El Niño as part of the broader El Niño-Southern Oscillation climate pattern. During a period of La Niña, the sea surface temperature across the equatorial Eastern Central Pacific Ocean will be lower than normal by 3–5 °C.

La Niña results in wetter-than-normal conditions in Southern Africa from December to February, and drier-than-normal conditions over equatorial East Africa over the same period.

The catastrophic drought in East Africa results from cooler waters on the other side of the globe. La Niña conditions in the tropical Pacific dry up the rain in East Africa. The drying influence of the latest La Niña over East Africa prolonged what was already a severe drought. Now two years of crop failures have left the region in a state of famine, as the United Nations recently declared.

Climate change is adding further complexity to the situation.

Heavy rain has caused widespread flooding across South Africa earlier this year. Heavy rainfall is common during La Niña summers in South Africa, and rainfall for the month of January 2011 has been nearly 10 times average in parts of the country.

More than 100 people have lost their lives in flooding across South Africa. The heavy rain has been widespread across the country.

NOAA, indicated in its latest update that La Niña is back. La Niña is usually associated with more rain in Southern Africa, but it is very difficult to predict the impact. Based on the latest update on ENSO, there is a strong chance that many parts of the region could be in for normal to above-normal rains later this season.

Whether this will indeed be the case need to be seen.