El Nino Returns

Some major changes have been occurring in the tropical Pacific. Most of the last winter was characterized by La Nina conditions in which the surface temperatures of the central/eastern tropical Pacific were cooler than normal. But recently there has been a shift to the opposite, El Nino, where the water in that region is warmer than normal. The plot below shows sea surface temperature for several areas in the tropical Pacific..the Nino 3.4 region is the one of most interest. There is a cycle between El Nino and La Nina called ENSO (El Nino Southern Oscillation) that has a period of roughly 3-7 years.


My profession has a variety of ways to predict the future of El Nino and La Nina, the two main ways being dynamical (full physics) and statistical models. The results of these models is shown below (Note that positive is El Nino side). Most models are going for warming (El Nino), although some (mainly the statistical models) are going for a neutral (near zero temperature anomoly from normal)...also called La Nada years.


So why do we care about El Nino and La Nina? Because there is a modest correlation with our weather, particularly during the winter. La Nina years tend to have more cold and snow (like last year!), while El Nino years tend to be drier, with less snow in the lowland and mountains, and weaker storms. I would hesitate to buy an annual ski pass at Snoqualmie Summit if the El Nino strengthens (but don't tell them I said that). And one more thing...during El Nino years southern CA tends to be much wetter than normal.