The prolonged La Niña phenomenon, which has affected temperatures and precipitation and exacerbated droughts and floods in various parts of the world, is likely to continue at least through August and possibly into fall and early winter in the Northern Hemisphere. This is according to a new update from the World Meteorological Organization.
Some long-term forecasts even suggest that it could persist until 2023. If so, this would be only the third « triple-dip La Niña » (three consecutive winters of La Niña conditions in the Northern Hemisphere) since 1950, according to the WMO.
La Niña refers to the large-scale cooling of surface temperatures in the central and eastern equatorial Pacific Ocean, associated with changes in tropical atmospheric circulation, namely winds, pressure and precipitation. It generally has opposite effects on weather and climate to El Niño, which is the warm phase of the El Niño Southern Oscillation (ENSO).
The current drought in the Horn of Africa and southern South America bears the hallmarks of La Niña, as do above-average precipitation in Southeast Asia and Australasia and predictions of an above-average hurricane season in the Atlantic.
However, all natural climate events are now occurring in the context of human-induced climate change, which is increasing global temperatures, exacerbating extreme weather and climate events, and influencing seasonal precipitation and temperature patterns.
« Human-induced climate change is amplifying the effects of natural phenomena such as La Niña and increasingly affecting our weather patterns, including increased heat and drought and the associated risk of wildfires, as well as record precipitation and floods, » said WMO Secretary-General Petteri Taalas.
The current La Niña event began in September 2020 and continued through mid-May 2022 in the tropical Pacific.
The oceanic components of La Niña weakened temporarily in January and February 2022, but have strengthened since March 2022.
The WMO Global Long Range Forecast Production Centers indicate that there is about a 70% chance that current La Niña conditions will continue through the boreal summer of 2022, and about 50-60% through July-September 2022.
There is some evidence that the probability may increase again slightly during the boreal fall of 2022 and early boreal winter of 2022-23.
Global Seasonal Climate Outlook
El Niño and La Niña are important drivers-but not the only ones-of the Earth’s climate system.
In addition to the long-established ENSO update, the WMO now publishes regular Global Seasonal Climate Updates (GSCU), which incorporate the influences of all other major climate drivers such as the North Atlantic Oscillation, the Arctic Oscillation and the Indian Ocean Dipole.
Despite the persistence of La Niña in the central and eastern equatorial Pacific, well above average sea surface temperatures elsewhere are expected to dominate the air temperature forecast for June-August 2022. However, the magnitude and strength of the projected warming is less than during the March-May 2022 period, according to the GSCU. The models indicate an increased risk of negative dipole in the Indian Ocean (IOD) between June and August 2022.
Precipitation forecasts are similar to typical La Niña rainfall effects.
