La Niña Resurfaces; More Extreme Weather?

NOAA said on Sept. 8, 2011, that the La Niña weather pattern has returned already, after the last La Niña cycle ran from June 2010-May 2011. During that period, the US bore the brunt of extraordinarily frequent and damaging extreme weather. It may be useful to keep close tabs on the weather as the new La Niña cycle begins.

NOAA is expected to issue its winter forecast in mid-October 2011, but the agency says the typical La Niña pattern, which hinges on below-normal temperatures in portions of the tropical Pacific Ocean, is linked with above-average temperatures and below-average precipitation in much of the southern tier of the country, and below-average temperatures and above-average precipitation in portions of the northern tier of the country. If those patterns pan out, that could lead to more drought and fires in the south, and blizzards and flooding in the north.

• "NOAA's Climate Prediction Center: La Niña is Back."

This is only the second time since 1950 that La Niña has returned within a few months of the end of the previous La Niña cycle. The other year was 2000.

• Cold and Warm Episodes by Season; Changes to the Oceanic Niño Index.

For extensive background information on La Niña, see:

• NOAA La Niña Page.

For more information on the recent spate of extreme weather, see the TipSheet of Aug. 31, 2011.

As the last La Niña tailed off, the US endured the second-hottest summer (June-August) in its history, just 0.1 degrees below the record in 1936 (amid the Dust Bowl years), according to another Sept. 8, 2011, press release from NOAA. August alone also was just 0.1 degrees below the all-time record, set in 1983.

• "U.S. Experiences Second Warmest Summer on Record."

AZ, CO, LA, NM, OK, and TX set their all-time August heat record. The latter four states also had their hottest summer on record. Not a single state had a below-average August temperature. Relative summer residential energy demand was the highest it's been since officials began keeping that statistic in 1895. The drought in Texas is as bad as it has been in 460 years, according to tree ring records.