Natural disasters

Torrential downpour

What is localized torrential rain?

It is heavy rainfall that is accompanied by the formation and significant development of cumulonimbus clouds with precipitation of tens of millimeters. It occurs suddenly in a short period of time (usually more than ten minutes) and over a very small area. These sudden downpours can be very dangerous, such as occurred in July 2008, when five people were killed in the swollen river of Togagawa in Kobe City, Hyogo Prefecture, and, in August of the same year, five people were killed by flooding inside a sewer pipe in Toshima Ward, Tokyo.

The mechanism of its occurrence is as follows. The air near the ground surface is warmed by the sun, etc., becomes light and begins to ascend, producing an upward current. In some cases, the upward current is intensified by the “warm, humid air that flows to the ground surface” and the “cold air that flows to the upper air.” Under this unstable atmospheric condition where warm humid air near the ground surface ascends, clouds are formed and keep developing to produce a cumulonimbus cloud, which further develop and bring about torrential rain in a localized area.

Click here for the Meteorological Observatory's leaflet “To protect yourself from localized torrential rains.”

Click here for video on torrential downpours.

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Related links

Disaster information from the Ministry of Land, Infrastructure, Transport and Tourism of Japan

List of multilingual medical institutions Sendai International Relations Association

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