NOAA Makes it Official: La Niña Conditions Have Ended

Published: June 9th, 2011

Leaving a trail of drought, flooding, and possibly even record tornadoes in its wake, La Niña was finally declared dead today by the National Oceanic and Atmospheric Administration (NOAA). The declaration was based on the fact that ocean surface temperatures in the tropical Pacific Ocean have pretty much returned to normal. Ocean temperatures had been running about 2.5°F lower through much of fall and winter 2010. La Niña is characterized by an area of cooler than normal water in the tropical Pacific, as well as altered trade winds and rainfall patterns.

Map of tropical Pacific Ocean sea surface temperature departures from average in August 2010, showing the cool conditions that are the hallmark of La Niña. Credit: NOAA/IRI.

While the extreme weather makes consistent news headlines, La Niña itself doesn’t get as much time in the spotlight. But all weather takes shape within the broader landscape of climate. Or to use a boxing analogy, climate is the trainer, but weather throws the punches.

The tropical Pacific progressively cooled through the spring and summer of 2010, and the first advisory for the 2010-2011 La Niña was issued on Aug. 5, 2010. By January 2011, La Niña was helping usher in heavy rains and flooding in Queensland, Australia as well as flash floods and landslides north of Rio de Janeiro in Brazil. In Sri Lanka, ongoing rains and flooding displaced more than a quarter million people from their homes, and swamped much of the rice-growing region of the country.

La Niña events typically last approximately nine to 12 months. And this one was no different. However, some episodes, like the 1999 to 2001 event (dubbed by some scientists as the “La La Niña”) persist for as long as two years.

It’s important to keep in mind that all weather events are now also born into a warmer world. This long-term warming trend, also known as global warming, stacks the deck for more extreme weather events — which suggests that extreme weather could dominate the headlines for years to come.

Typical winter weather pattern during a La Niña winter. Credit: NOAA/CPC.

It’s unclear how global warming is influencing natural climate cycles, such as La Niña and its sibling, El Niño. However, some studies do show shifts in these cycles that may be tied to climate change.

And La Niña is pretty robust and predictable in terms of the type of weather we expect due to its influence on the jet stream. On average, La Niña winters are warmer than normal in the Southeast and colder than normal in the Pacific Northwest. La Niña also features drier than normal conditions in the Southwest, Central Plains and Southeast. In contrast, the Pacific Northwest is more likely to be wetter than normal in the late fall and early winter. Judging by NOAA's maps of precipitation anomalies for fall 2010 and winter 2011, the signature of La Niña is pretty clear.

Posted in Impacts, Climate, Extremes, Drought, Flooding, Weather, Extreme Weather, Global, United States, US National, Extreme Planet

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Comments

By Mauri Pelto (West Boylston)
on June 11th, 2011

The interesting thing about this year’s La Nina is that it had a number of aspects that do not fit the typical pattern. A look at the winter temperature and precipitation anomalies at your last NOAA link indicate several
1) That the wettest area with respect to normal was the northern Great Plains.
2) That the southeast had a cool winter.
3) That Central and southern California was quite wet and the adjacent sierra snowy, as Alyson Kenward discussed this week.
4) That the northeast was quite wet.

By Steve
on June 11th, 2011

This article is difficult to understand. It says:

La Nina is over “based on the fact that ocean surface temperatures in the tropical Pacific Ocean have pretty much returned to normal. Ocean temperatures had been running about 2.5°F higher through much of fall and winter 2010.”

Ok, La Nina is warmer ocean temps. Then it says:

“La Niña is characterized by an area of cooler than normal water in the tropical Pacific”

Huh?

By Andrew
on June 11th, 2011

Steve,

You’re absolutely right. It should read (and now does) “Ocean temperatures had been running about 2.5 deg F lower through much of fall and winter 2010.” Sorry for the typo!

-Andrew F.

By Rebecca (Rising Star, Texas 76471)
on August 2nd, 2011

Desperate for relief in Texas! When do you predict a break in our current weather pattern? This July we broke many records. The hottest summer on record. Almost all of our lakes are dangerously low and many of our stock tanks are dry. Ranchers are selling off their cattle due to lack of grass to graze and little or no water. Any information that you could send me via email or otherwise about our current “la Nina” would be appreciated.

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Andrew Freedman

Andrew Freedman is a senior science writer for Climate Central, focusing on coverage of extreme weather and climate change. Prior to working with Climate Central, Freedman was a reporter for C...