La Niña's back
What can you expect for weather this winter? Much the same as last season, says the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center. You can either thank – or curse – La Niña for that, because it's the influence that's been driving the weather like a drunken sailor during the last year. Pacific Ocean temperatures are forcing the jet stream to take a far northerly route that brings colder-than-normal temperatures to northwestern states, the promise of loads of snow to the Midwest, and the curse of continued severe drought to southern states.
La Niña was wreaking havoc on weather across the globe early in 2011, and then it disappeared last summer only to reappear early last fall.
“This means drought is likely to continue in the drought-stricken states of Texas, Oklahoma, and New Mexico,” says Mike Halpert of the Climate Prediction Center. “La Niña also often brings colder winters to the Pacific Northwest and the northern Plains, and warmer temperatures to the southern states.”
A strong La Niña during 2010-11 contributed to record winter snowfall, spring flooding, and drought across the U.S. It also prompted other extreme weather events throughout the world, such as heavy rain in Australia and an extremely dry equatorial eastern Africa.
During a La Niña episode, cooler-than-average Pacific ocean temperatures influence global weather patterns. La Niña typically occurs every three to five years. Back-to-back episodes occur about 50% of the time.
The blistering heat experienced by the nation marks the second-warmest summer on record according to the National Climatic Data Center. Persistent heat and lack of rain caused a record-breaking drought across the southern states. Actually, the entire nation suffered in August when the average U.S. temperature was 75.7°F. That is 3°F. above the long-term (1901 to 2000) average. Summertime temps averaged 74.5°F., which was 2.4°F. above average.
How hot was it?
To makes matter worse, southern states recorded their warmest August on record. Severe drought now covers one third of the country with parts of Louisiana, New Mexico, Oklahoma, and Texas experiencing a drought of greater intensity (but not yet duration) than those of the 1930s and 1950s. An analysis of Texas statewide tree-ring records dating back to 1550 indicates that the summer 2011 drought in Texas is matched by the summer of 1789.