2006 El Nino conditions, as observed by the Jason satellite. Photo: NASA

The ocean conditions formally known as ENSO, or the El Nino/Southern Oscillation, arise when normal upwelling of deep, cold water abates, causing warmer surface temperatures (SST).

El Nino and its opposite, La Nina, have far-reaching implications on weather patterns. Here on the West Coast, it usually means wetter winters in southern California and drier ones in the Pacific Northwest.  Because northern and central California lie in between, things there can go either way.

El Nino can also have a significant impact on fisheries, as much of the food chain is interrupted when upwelling slows.

Here’s a good overview of El Nino “mechanics” from UC Berkeley.