The La Nina pattern, linked to one the most extreme weather years on record in 2011 in the U.S., is forecast to fade away this spring according to the National Oceanic and Atmospheric Administration (NOAA).
La Nina is characterized by cooler than average waters in the equatorial Pacific, and NOAA finds the seas are warming in the eastern Pacific.
“A majority of models predict La Niña to weaken through the rest of the Northern Hemisphere winter 2011-12, and then to dissipate during the spring 2012,” NOAA wrote in an advisory released today.
Via NOAA’s Environmental Visualization Laboratory: NOAA’s POES satellites measure the temperature of the ocean surface - one of the primary indicators of the El Niño-Southern Oscillation (the climate cycle that changes between El Niño and La Niña every few years). This time-series shows the evolution of the most recent La Niña, which is currently weakening in intensity.
La Ninas often feature a strong northern jet stream in the U.S., which drives cold, stormy weather into the northern tier while dry, warm conditions bubble up in the South Central and Southwest. 2011’s La Nina pattern was tied to the historic drought conditions in Texas and flooding from the northern Plains through the Mississippi Valley. Not to mention, the pattern promoted highly volatile conditions at the intersection of the cold/wet and warm/dry extremes, leading to the historic tornado season from the Midwest to Southeast.
NOAA cautions, that although La Nina is likely to conclude this spring, its impacts may linger:
....we expect La Niña impacts to continue even as the episode weakens. Over the U.S. during February - April 2012, there is an increased chance of above-average temperatures across the south-central and southeastern U.S., and below-average temperatures in the northwestern U.S. Also, above-average precipitation is favored across most of the northern tier of states (except the north-central U.S.) and in the Ohio and Tennessee Valleys, and drier-than-average conditions are more likely across the southern tier of the U.S.
In other words, through the first half of 2012, we might see a continuation of the kinds of weather extremes that plagued 2011. Perhaps by the summer, a different regime will settle in.