After a short absence, climate troublemaker La Niña is back, and forecasters say it could have a big impact on the winter weather outlook.
La Niña is a part of a natural climate cycle officially known as El Niño-Southern Oscillation, called ENSO by scientists. The cycle swings between warmer and cooler seawater in a region along the equator in the tropical Pacific Ocean. La Niña is marked by cooler-than-average ocean water in the region.
Those subtle changes can have big ripple effects across the globe's climate, with the cycle at times upping the chances for rain, drought, hurricanes and other chaos. The effects vary drastically by region, even within the United States.
Ancient El Niño? Mysterious climate cycle blamed for millennia of chaotic weather.
Impacts from a typical La Niña cut across the continental United States, having opposite effects in the south and north — and causing unpredictability in the heavily populated Northeast corridor.
