Dairy Herd Management has one of the best discussions I have seen about the end of the current El Niño and what is likely to happen with the coming La Niña. It’s written in a general way, not geared to livestock, so crop producers and foresters should read it too. Here’s the link.
Unlike El Niño, La Niñas often last more than one year, and so we may be able to predict with some accuracy the climate as far out as 2019, although of course the farther out you get, the less certain things become. In the Southeast, La Niñas are often associated with drought conditions because (statistically) the dry and warm winters that come with La Niña often set up the beginning of our growing season with a deficit of soil moisture that is almost impossible to overcome once the warm summer begins and warm temperatures ramp up evaporation of any rain that falls.
If you look at the graph of the Oceanic Niño Index (ONI) and compare it to recent years, you can see that 1998-2001, 2007-2009 and 2011-2013 were all time periods when the ONI was quite negative, indicating a strong La Niña. Those are also periods when extreme drought was seen in parts of the Southeast, although the area with the worst impacts was different in each drought. The period from 1954-1956 was also a period with a strongly negative ONI, and that was a time of terrible drought in the Southeast and other parts of the US. The green arrows denote periods when a strong El Niño was followed by several years of La Niña, and this year’s El Niño has certainly been one of the strongest on record.
