Super El Niño Could Bring Extreme Heat to Japan This Summer

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This summer could bring some of the most intense heat Japan has ever experienced, with temperatures of 40°C (104°F) or higher possible in many parts of the country, according to Yoshihiro Tachibana, a professor of meteorology at Mie University.

The forecast comes as an El Niño event has developed in the Pacific. Although El Niño typically brings cooler summers to Japan, conditions this year could be different. Sea surface temperatures around the Philippines have remained unusually warm, likely due to the effects of global warming.

How a Typical El Niño Works

According to the Japan Meteorological Agency, El Niño occurs when sea surface temperatures in the eastern tropical Pacific off the coast of Peru remain at least 0.5°C above average for six months or longer.

The phenomenon occurs when the easterly trade winds that normally blow across the Pacific weaken. This allows warm waters near the Philippines to move eastward toward South America, leaving cooler waters behind in the western Pacific.

The cooler waters around the Philippines weaken rising air currents and reduce cloud formation. This, in turn, weakens the Pacific high-pressure system east of Japan, preventing it from extending over the country and making cooler summer conditions more likely.

In June, the Japan Meteorological Agency said El Niño appeared to have emerged in spring and was expected to continue into autumn.

Super El Niño Could Intensify Heat

However, Tachibana said sea surface temperatures around the Philippines, which would normally cool during an El Niño event, have remained unusually high this year.

The warmer waters could fuel stronger rising air currents, helping to reinforce the Pacific high-pressure system. As the system expands over Japan, it could bring prolonged periods of extreme heat.

If sea surface temperatures in the central and eastern tropical Pacific rise more than 2°C above average, the event could develop into what is known as a "super El Niño," an exceptionally strong El Niño event capable of causing major shifts in global weather patterns.

During a super El Niño, warmer waters near the Philippines can generate powerful upward air currents. These currents descend around Japan, contributing to the strengthening of the Pacific high-pressure system.

The stronger high-pressure system can then expand over Japan, increasing the likelihood of extreme temperatures.

Tachibana warned that this summer's heat could reach "unprecedented levels, with extreme heat days occurring one after another across many parts of the country."