Monitoring the surface temperature of the Pacific Ocean, conducted by U.S. experts, marks the progression of La Niña in October 2011.
Such an event is unexpected and contrary to the typical cycling of natural fluctuations. Southern Oscillation cold phase was completed last spring, and after a neutral phase usually comes warm episode — El Nino. The resumption of the La Niña phase after a short neutral from meteorologist has been called "ragged La Niña." Over the past 60 years, this was observed only once — in 2008-2009. According to calculations Climate Prediction Center (USA), La Niña will intensify and will last through the winter.