Record-setting spring temperatures raise likelihood of steamy hot summer in Japan

The average temperatures in Japan's Tohoku, Kanto-Koshin, Tokai and Kinki regions during the previous March set all-time records.

What's more, reports Weekly Playboy (June 11), in April, the average temperatures for April in Kanto-Koshin surpassed the previous all-time high by 2.7 degrees.

On May 16, the mercury in Fukushima City set a new record of 32.9 degrees. The same day, Toyama City posted 32.8 degrees, and Tomioka City, Hyogo Prefecture, 32.6 degrees. Out of 930 weather monitoring locations in Japan, 188 reported temperatures above 30 degrees and over 700, temperatures above 25 degrees. All of these stand as new records.

Weekly Playboy asked meteorologist Yukiko Katayama what caused this year's spring to overheat. "According to the Meteorological Agency, the westerly has been flowing at a higher latitude than in normal years, allowing warm air from the south to move in," she explained. "There have been more sunny days as well."

So then...does this mean we're in for a sizzling summer?

"Yes, I think so," she replied. "More than during average years, there's a likelihood that two high-pressure systems will be situated over Japan, to a greater degree than in average years. One will move up from the southeast. The other is the Tibet high-pressure system that's situated over the Tibetan plateau. Its high pressure is generated from heat by the sun while at an altitude of 5,000 meters or higher."

According to Katayama, it's is looking like portions of the two systems will overlap, making for continued hot, sunny summer days with high humidity.

Another factor has been the the La Niña phenomenon, which has seen lower than average ocean temperatures in the central Pacific, resulting in irregular weather patterns around the world. In Japan's case, from last autumn the westerly that typically meanders at a higher latitude moved to the south, resulting in a particularly cold winter -- with record-setting low temperatures during February.

The presence of higher ocean temperatures in the vicinity of the Philippines activate tropical cumulonimbous clouds in the western Pacific, which may push the high-pressure systems toward Japan.

"La Niña was supposed to have ended this spring, but its influence remains, and there's a strong chance the water temperatures around the Philippines will stay high," Katayama added.  

So then what, Weekly Playboy wants to know, is in store for Japan this summer?

Katayama can't be entirely sure, although she cites a prediction from the government's Meteorological Agency that this year's summer will be "hotter than average."

"Based on this year's spring, we can see a continuing warming trend since the year 2000, with rising averages. Of course, with global warming we have to consider that all four seasons will be affected."

The summer of 2009 was characterized by a high-pressure system off the Sea of Okhotsk, and due to prevailing winds, temperatures wound up dropping by 0.2 degrees below seasonal average. Any chance of that happening again this year?

"We generally only know about such things two weeks before they occur," Katayama says. She also pointed out that the agency's forecast for a relatively cool April was way off. "The three straight warm months this spring surprised me too."

In any event, if you look at years when two high-pressure systems made their presence felt over Japan, they made for record-breaking high temperatures. Such was the case in the summers of 2004 and in 2013. Will 2018 be the year when Tokyo posts record highs exceeding -- shudder! -- 40 degrees?

At any rate, we'll be finding out soon enough, the article concludes.

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