La Niña is part of a natural climate cycle that can cause extreme weather across the planet. It is likely to last for another five months and bring devastating weather
A worldwide extreme weather event looks set to hit this autumn, lasting for around five months.
Forecasters say this La Niña should be a “weak” version of the phenomenon, before adding there is no real guarantee of how it will play out and some places will be more badly affected than others. La Niña is part of a natural climate cycle that can cause extreme weather across the planet.
La Niña is the cool phase of the El Niño-Southern Oscillation – a naturally occurring global climate pattern that involves changes in wind and ocean temperatures in the Pacific Ocean. Experts say northern parts of South America could see more rain than usual.
Southern regions of the USA and parts of Mexico could be drier than average, but the northern tier of the USA and southern Canada could be wetter than average, the forecasters are predicting. The National Oceanic and Atmospheric Administration’s Climate Prediction Centre in the US, says there is a 60% chance that a weak La Niña event will develop this autumn and could last until March.
El Niño is the warm phase and happens when trade winds that typically blow across the Pacific toward Asia weaken, allowing warm ocean waters to pile up along the western edge of South America. But during La Niña, the trade winds intensify and cold water from the depths of the sea rises up, resulting in cooler than average ocean temperatures in the eastern Pacific.
These cold ocean temperatures and changes in the atmosphere affect the position of the jet stream — a narrow band of fast moving air flowing from west to east around the planet — by bumping it northward. The jet stream sits over the ocean and can tap into its moisture, influence the path storms take and boost precipitation.
Michelle L’Heurex, a climate scientist at the NOAA, explained that La Niñas tend to last longer and be more recurrent than El Niño events. “We had three back to back winters where we had La Niña conditions, which was unusual because the only other case of that happening was back in 1973 to 1976.”
Climate scientist at the NASA Goddard Institute for Space Studies Ben Cook said the forecast for this autumn is “unusual although it’s not unprecedented”. He aded that frequency of La Niña events can be stressful for regions that have been dealing with drought lately, such as East Africa. “If we’re moving into another La Niña event, it means kind of a continuation of those really bad conditions.”
