JMA to release forecasts for rain that could cause severe flooding

The Japan Meteorological Agency will start releasing forecast information about linear rainbands, called “senjo kosuitai,” from June that could give the public major flooding warnings. 

“Once linear rainbands occur, they will likely lead to a disaster,” said Naoyuki Hasegawa, head of the agency, at a news conference. “Once the information is released, I want people to prepare for a massive rainfall disaster.”

The new forecast information will divide Japan into 11 wide areas, according to the details that the agency revealed on May 18.

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The information will be available on the agency’s website.

The new system is expected to help residents evacuate quickly and local officials prepare for a disaster.

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Data for water vapor amounts is needed to forecast linear rainbands, but they have been difficult to foresee it due to a lack of observation equipment.

The agency has built an observation network and utilized the Fugaku supercomputer, which was jointly developed by the Riken research institute and Fujitsu Ltd., to forecast linear rainbands.

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The agency said it will continue to improve the accuracy and hopes to issue a forecast warning 30 minutes before linear rainbands are formed.

The agency aims to make available the degree of danger on a municipality basis in 2029.