Both the Australian Bureau of Meteorology and the US National Oceanic and Atmospheric Administration have upgraded their outlook from alert to ‘La Niña’ this week.
However, the effects of La Niña can vary considerably depending on its duration, intensity and time of year. Most models suggest this winter’s La Niña will be weak and short-lived and its potential impacts are still uncertain.
La Niña occurrence from December to February typically correlates with poor crop production in Brazil and Argentina and could delay planting of the productive second crop of their season. Dry conditions have been observed in Argentina this November which could affect maize and soyabean yields if they continue. La Niña over (N Hemisphere) winter is also associated with wetter than normal conditions in South East Asia which could affect palm harvesting.
After a difficult wet autumn, farmers in Scotland, Northern Ireland and Cumbria are reporting significant shortfalls in forage stocks for winter. Although feed prices are currently stable, if they begin to move then these farmers could be particularly exposed.
Note: La Niña periods in the above graph are based on a threshold of -0.5oC for the Oceanic Niño Index (ONI), a 3 month average of sea surface temperature anomalies in the Nino3.4 region, as defined by the NOAA. The ONI is one measure of the El Niño-Southern Oscillation, and other indices can confirm whether features consistent with a coupled ocean-atmosphere phenomenon accompanied these periods.