By Pam Knox
After two winters of dry conditions in Georgia due to La Niña, El Niño appears to be returning to the Eastern Pacific Ocean. This is good news for farmers in drought-stricken areas of the state, who have suffered from lack of soil moisture due to dry winters the past two years.
El Niño and La Niña are opposite phases of an oscillation in ocean temperature along the equator in the eastern Pacific Ocean. In an El Niño, warmer-than-usual water off the coast of Peru and Ecuador cause development of strong thunderstorms over the warm water which act like a "rock" in the global air circulation, diverting the high-level winds into different paths.
In El Niño winters, the subtropical jet stream, which pulls water vapor from the tropics into Georgia, shifts so that it is located right over southern Georgia, bringing clouds with associated cooler temperatures and rain into the state. In La Niña, the opposite happens; the jet stream shifts north, leaving Georgia, particularly the southern regions, warmer and drier than usual.
Pacific Ocean temperatures have been slowly climbing over the past few months, and a full-fledged El Niño is predicted to start in September or October. Once it develops, it will most likely stay around until late winter or early spring. The wetter-than-usual conditions associated with El Niño in the winter months means that precipitation is usually able to sink into the soil since evaporation is low during the winter months. This improves soil moisture across the area going into the next growing season.
Knox is an agricultural climatologist with University of Georgia Cooperative Extension.