Photo/IllutrationFirefighters and other rescue workers search houses hit by a landslide and swept into the sea off Uwajima, Ehime Prefecture, on July 7. (Eiji Hori)

The record-breaking rainfall that has soaked wide areas from western to eastern Japan is mainly blamed on a seasonal rain front that has remained longer over the region than in conventional years.

“It is the typical condition of the last period of the rainy season,” said an official of the Japan Meteorological Agency (JMA).

This time, however, Typhoon No. 7, which passed through the Sea of Japan earlier this month, also brought with it wet air, which led to the deadly torrential rainfall.

The amount of precipitation of the past 48 hours stood at 919.0 millimeters in Umaji, Kochi Prefecture, as of 8 p.m. on July 7, the most recorded on that day.

It was followed by 683.0 mm in Gujo, Gifu Prefecture, and 581.5 mm in Saga.

More than 100 locations marked record precipitation mainly in western Japan, including Hiroshima and Okayama prefectures.

The seasonal rain front is likely to gradually weaken from July 8. But torrential rain could still fall intermittently.

The soil and slopes may have become weakened due to saturation from the heavy rain that has fallen so far. As landslides could occur even with a small amount of rain, it is necessary to continue to take precautions.

The amount of precipitation in the past 48 hours serves as criteria on whether to issue an emergency warning against heavy rain.

An emergency warning is issued only when extremely heavy rain that occurs only once in several decades is predicted.

The JMA issued the emergency warning to a total of nine prefectures from July 6 to 7. Of the nine, only Gifu Prefecture was still subject to the warning on the morning of July 8. At 2:10 p.m. on that day, however, the warning to the prefecture was also lifted.

But the JMA newly issued the emergency warning to Kochi and Ehime prefectures on July 8.

As a result, the total number of prefectures that were subject to the warning increased to 11.

However, the warnings issued to the two prefectures were also lifted at 2:50 p.m. that day.

For current emergency weather warnings from the Japan Meteorological Agency: http://www.jma.go.jp/jma/indexe.html