Typhoons travel much slower and cause more damage around the Japanese archipelago in September, a trend that could worsen due to global warming, researchers said.
“As global warming progresses, the combined effects of slower typhoons and heavier downpours could wreak havoc,” said Munehiko Yamaguchi, senior researcher at the Meteorological Research Institute of the Japan Meteorological Agency.
Scientists at the institute and elsewhere studied typhoon speeds between 1980 and 2019 by region and month.
The results showed that typhoons that roamed the Tokyo metropolitan area in September were 35 percent slower over the past two decades than they were in the first 20 years of the study.
The speed decline rates were 33 percent for Osaka Prefecture and 26 percent for Okinawa Prefecture, they said.
The slower speeds extend the country’s exposure to heavy rain and winds from the storms.
One factor cited in the study is that autumn weather arrives later due to global warming, resulting in weaker prevailing westerly winds that can drive typhoons away.
Computer simulations of the effects of climate change suggest that typhoons that reach Japan travel more slowly not only in September but also in October.
Huge storms were reported in 2019, such as Typhoon No. 15, which caused severe damage mainly in Chiba Prefecture, and Typhoon No. 19, which recorded record rainfall, were 40 percent slower than conventional years.