COLLEGE PARK, MARYLAND — The U.S. Climate Prediction Center said on Thursday, September 11 that the weather pattern known as La Nina had officially formed.
La Nina — which means "little girl" in Spanish — is a complex ocean-atmosphere phenomenon that occurs every few years in the Pacific Ocean.
La Nina brings dry, warm weather to the Southwestern U.S. It brings cool, wet weather to an area reaching from the Pacific Northwest and southeastern Alaska to the Northern Plains and central Canada.
Under normal conditions, winds in the Pacific Ocean push warm water from the west coast of South America toward Indonesia.
As the warm water moves westward, cold water rises.
When La Nina occurs, winds in the Pacific grow much stronger.
They push even more warm water toward Indonesia, causing more cold water to rise near the west coast of South America.
This could worsen the drought in the Southwestern U.S. this winter, while bringing a cooler, wetter winter to other parts of North America.
These changes in sea surface temperature are felt around the planet.
La Nina can lead to more rain in Australia and Indonesia, stronger hurricanes and typhoons, and more lightning in some parts of the world.