Two weeks after deadly Typhoon Hagibis flooded millions in Japan, more heavy rain looms

A man dumps debris caused by Typhoon Hagibis, in Nagano, central Japan last week. Parts of the country look set to be hit by heavy rain again, bought in by Typhoon Bualoi. Photo / AP

Two weeks after Typhoon Hagibis killed more than 80 people in Japan with flooding and landslides, the same hard-hit areas on Honshu Island may experience dangerous flooding again, because of a heavy rain linked to Typhoon Bualoi. Significant rainfall is forecast to begin along the eastern coast of Honshu, which includes Tokyo, as early as Thursday.

Bualoi, which scraped the Northern Mariana Islands on Tuesday, currently has maximum sustained winds of 185kmh, making it the equivalent of a Category 3 storm as it churns well south and east of Japan. Both its strongest winds and heaviest rainfall are expected to remain offshore, passing several hundred miles to the east of Tokyo on Friday.

Light rain was already falling late Wednesday local time across much of Kyushu and was soon to overspread into Shikoku in southwestern Japan.

TROPICAL UPDATE: This infrared image from #NOAA20 shows #TyphoonBualoi continuing to spin in the #Pacific. #Bualoi, which means "floating lotus" in Thai, is now the equivalent of a #Category4 #hurricane in the #Atlantic. Get the latest here: https://t.co/M5KcNCG8hC pic.twitter.com/yxriRUmWK1

— NOAA Satellites - Public Affairs (@NOAASatellitePA) October 22, 2019

A rich stream of moisture from Bualoi will curl westward out of the storm, drawn into a nontropical low swirling up the spine of Japan and paralleling the typhoon. That will focus a band of heavy downpours that will ripple along Japan's eastern shore.

Uncertainty exists as to how close this band sets up relative to Japan's coastline. Some computer models - such as the European - show the heaviest rain falling just to the east of Japan. Nevertheless, that model still shows more than half a foot of rain falling in spots that were hit hard during Hagibis, which set multiple rainfall records for the country.

Bullet trains submerged in muddy waters in Nagano, central Japan on October 13, after Typhoon Hagibis hit the city. Japan could be hit by more heavy rain bought by Typhoon Bualoi. Photo / AP

Other models, such as the American GFS, aggressively bring the heaviest rain farther inland with isolated rain totals topping 25cm in spots. The mountains, which act as a barrier to incoming moisture that can squeeze out copious amounts of rainfall, could receive far higher amounts.

The most likely spot for these orographically induced higher totals is in the Akaishi and Kiso Mountains, especially in southern areas. Nearby Hakone, a few miles from Mount Fuji, received 94cm during Hagibis, setting a record for that location and marking one of the highest calendar-day rainfall totals in Japanese history.

Particularly affected may be Chubu and Kanto, especially the Izu Peninsula, where Hagibis made landfall October 12.

If heavy rain falls on steep terrain already loosened by Typhoon Hagibis, there will be renewed threats of dangerous landslides as well.