A patch of the Pacific Ocean has been quietly warming again, drawing attention from meteorologists who spend their time watching patterns most people never think about. The signals are not dramatic on their own: a few degrees here, a shift in sea surface temperatures there, winds behaving slightly differently than expected.

A potentially strong El Nino could be officially declared this week and experts warn it could bring major weather shifts across the US.

El Niño is characterized by a warming of the Pacific Ocean that alters global weather patterns, which can damage crops and strain power grids. | World News