The strongest El Niño in history is anticipated. El Niño refers to a phenomenon where sea surface temperatures in the equatorial eastern Pacific rise abnormally. Depending on the continent, it leads to climate disasters such as torrential rains (in South America, etc.) and droughts (in Australia, etc.), exerting a significant impact on global grain markets. While South Korea does not experience direct impacts, it tends to see heavy winter rainfall and high-temperature phenomena. The Korea Meteorological Administration (KMA, Administrator Lee Mi-sun) officially confirmed that El Niño has been occurring since May of this year, and announced on the 6th its forecast that the current El Niño will become the strongest on record.

The KMA determines the start of El Niño when the 3-month moving average of sea surface temperatures in the El Niño monitoring region remains 0.5°C or more above normal for 5 consecutive months or longer. This criterion has been met since May of this year. As sea surface temperatures continue to stay above normal, a strong El Niño is currently underway. The sea surface temperature anomaly for October stood at +2.6°C, and the 3-month (August–October) moving average anomaly was +2.4°C, both recording the highest figures on record for the same period. These are higher figures than during the same periods in 1997 and 2015, when past strong El Niños occurred. El Niño develops as trade winds weaken and the warm water pooled in the western Pacific expands eastward. It generally peaks during the winter season. This year, it is expected to reach its peak in December. Currently, the sea surface temperature anomalies in the monitoring zone are showing record-high levels for the same period. With high sea surface temperatures expected to be maintained moving forward, it is forecasted to develop into the strongest El Niño on record.

During winters when El Niño is well-developed, convective activity in the tropical western Pacific generally decreases, and an anticyclonic circulation is strengthened to the east of South Korea. Consequently, warm and humid air flows into South Korea, showing a tendency where winter temperatures are higher than normal and precipitation is generally greater. According to the KMA’s 3-month outlook (released on October 23), temperatures for November and December are expected to be higher than normal, and precipitation is generally forecasted to be higher than normal. For January of next year, temperatures are expected to be generally higher than normal, while precipitation will likely be similar to normal, though dramatic temperature variability is projected due to the temporary influx of cold air. South Korea's winter weather is influenced not only by El Niño, but also by various climate factors such as sea surface temperatures in the Indian and Atlantic Oceans, Arctic sea ice, and Eurasian snow cover. Depending on the status and interaction of these factors, changes in temperature and precipitation may vary. "Due to the influence of this winter's strong El Niño, temperatures are expected to be higher than normal and precipitation generally greater than normal," said KMA Administrator Lee Mi-sun. "As various climate factors act together, it is necessary to prepare for sudden weather changes such as heatwaves and cold waves. The KMA will closely monitor and analyze El Niño and the climate factors affecting South Korea to provide climate prediction information that helps citizens and relevant organizations prepare in advance."

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