Stationary front causes heavy rain in wide areas of Japan

The Japan Meteorological Agency said a group of thunderclouds developed in the northern part of the Izu island chain, south of Tokyo, causing downpours of up to 166 millimeters in three hours near Niijima.

In the 24 hour-period through Friday morning, 250 mm of rainfall is forecast in the Tokai region, as well as downpours of 150 mm in the Kanto-Koshin region, southern Kyushu, and the Amami region. In the Tohoku region, 60 mm is predicted.

The agency also alerted the public to possible wind gusts and lightning since warm and wet air has flown into the front, causing severe atmospheric instability.

Earlier in the week, the agency issued an alert over thunderclouds after they were observed over the southern island prefecture of Okinawa.

The Tuesday alert was the first based on a new heavy rain warning system, which started operating on June 17 and is designed to improve the accuracy of predicting areas of heavy rain.