Thursday, June 24, 2010

Long-Lasting La Niña Poised to Control Weather

Earlier this month the Climate Prediction Center (CPC) announced that we officially moved into a La Niña pattern, and recent images from NASA's Jason-2 oceanography satellite verify. The opposite of El Niño, La Niña is the cooling of the equatorial Pacific Ocean.

El Niño and La Niña play a major role in global weather. During a La Niña, trade winds in the western equatorial Pacific Ocean are stronger than normal, and the cold water that normally exists along the coast of South America extends to the central regions. La Niñas are associated with less moisture in the air, resulting in less rain along the coasts of North and South America. They also tend to increase the formation of tropical storms in the Atlantic.

So what exactly does that mean for the United States? What impact can we expect?
  • An increase in the number of tropical storms as a result of La Niña boosts the chances that a storm (or hurricane) will enter the Gulf of Mexico, home to about 30 percent of U.S. oil and 12 percent of U.S. natural gas production, as well as the anomaly of an oil slick this year.

  • La Niña's cooling pattern often brings dryer, warmer weather to the southern half of the United States, thus increasing the wildfire threat in Florida and California.

  • During La Niña, the northern third of the United States often has colder winters.

  • Increased rainfall in the Pacific Northwest is also common during La Niña.
Experts expect the central equatorial Pacific Ocean to stay colder than normal throughout the summer and beyond, so the risk for long-lasting La Niña-type weather conditions to affect North America in coming months is quite likely.

Looks like next winter could be VERY different from last, which was largely controlled by
El Niño!