La Nina conditions are likely to persist until April 2021, however the impacts may be felt beyond this timeframe. Countries of high concern include Kiribati, Tuvalu, parts of Solomon Islands and Papua New Guinea due to below-average rainfall that has persisted over the wet season, and could further be compounded by the onset of the dry season. Cyclone activity in the Western Pacific should also remain closely monitored.
What is La Nina?
La Nifia is a recurrent global atmospheric-oceanic phenomenon associated with a decrease in sea surface temperatures in the central tropical Pacific Ocean and a sustained strengthening of the trade winds. A La Nina event develops approximately every two to seven years and lasts from six months to two years. A global La Nina event is declared after the central Pacific Ocean and the atmosphere shows signs of certain atypical conditions for a prolonged period of time, usually over a period of three months. La Nina increases the risk of heavy rainfall and flooding in some parts of the world and of drought through reduced rainfall in others. In some instances, and for some regions, the impact of La Nina also depends on its interaction with other climatic events, such as the Indian Ocean Dipole.
The impact of La Nina on agriculture and food security can be significant. The event from 2010-12 caused the Pacific island nations of Tuvalu and Tokelau to declare a state of emergency due to drought which induced severe water shortages. This drought event was the strongest on record for both nations.
The extent of La Nina's impact on agriculture and food security depends on a complex interplay of meteorological, seasonality and vulnerability factors. As a result, impact patterns of global La Nina events are variable and do not necessarily materialize during every occurrence. While the intensity of a La Nina event generally affects the severity of its global impacts, there is always potential for even a weak or moderate episode to generate serious humanitarian impacts in some regions and on the agricultural sector. This uncertainty makes it especially critical to systematically analyze weather forecasts, identify vulnerabilities and determine risks with the help of regional and national climate outlooks, and strong early warning systems.
La Nina & the Pacific Islands
La Nina is officially underway in the Pacific, as confirmed by regional agencies such as Pacific Meteorological Desk Partnership at the Secretariat of the Pacific Regional Environment Programme (SPREP), the New Zealand National institute of Water and Atmospheric Research and Australia's Bureau of Meteorology. The impacts of La Nina will vary from country to country, and traditionally those in the Central and Eastern Pacific may be more susceptible to droughts, while countries in the South-West Pacific will become more prone to flooding and landslides, while tropical cyclones are more likely to form further west during this time. This is due to the South Pacific Convergence Zone, a band of intense rainfall which extends across the Pacific from the equator, being pushed South-West during La Nina.