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This winter's El Niño is shaping up to be the strongest ever recorded, raising the prospect of a warmer-than-normal season with frequent rain.
The Korea Meteorological Administration said Friday that the El Niño that began in May is expected to become the most powerful on record.
El Niño refers to the periodic warming of sea surface temperatures in the tropical Pacific Ocean. It is considered to have occurred when the three-month moving average of sea surface temperatures exceeds the seasonal norm by 0.5 degrees Celsius or more for at least five consecutive months.
The intensity of the current El Niño is already at an exceptional level. According to the Korea Meteorological Administration, sea surface temperatures in the El Niño-La Niña monitoring zone averaged 30.0 degrees Celsius from Oct. 11 to Oct. 17 — 3.3 degrees above the seasonal norm. A deviation of 1.5 degrees or more above normal is typically classified as a strong El Niño, meaning the current anomaly is more than double that threshold.
The sea surface temperature anomaly for October stood at 2.6 degrees, while the August-to-October moving average deviation reached 2.4 degrees — both the largest on record since reliable observational data became available in 1950. The figures surpass even those recorded during the strong El Niño events of 1997 and 2015.
El Niño develops when trade winds over the tropical Pacific weaken. Under normal conditions, trade winds blow from east to west, pushing warm surface water toward the western Pacific. When those winds slacken, the warm water that has accumulated in the western Pacific spreads back toward the central and eastern Pacific, raising sea surface temperatures and altering atmospheric circulation patterns.
El Niño itself is not a product of climate change — official records date back to 1881, and it is a natural phenomenon that has recurred for centuries. It does, however, affect weather patterns worldwide and can amplify global warming.
El Niño typically intensifies during winter, and the current event is forecast to peak in December. The Korea Meteorological Administration said sea surface temperatures in the monitoring zone are expected to remain elevated, allowing the phenomenon to develop into the strongest El Niño ever observed.
In its three-month outlook released Oct. 23, the agency forecast above-normal temperatures and above-normal precipitation for both November and December. For January, temperatures are expected to remain above normal while precipitation is forecast to be near average.
The agency cautioned that winter weather is influenced by a range of climate factors beyond El Niño alone — including sea surface temperatures in the Indian and Atlantic oceans, Arctic sea ice extent, and snow cover across the Eurasian continent — and urged the public to monitor the latest forecasts.
bbo@heraldcorp.com
