In order to mitigate the danger and damage caused by heavy rainfall, the Meteorological Agency will begin forecasting ¡°linear precipitation zones¡± starting Wednesday, as part of efforts to improve forecasting accuracy.

Linear precipitation zones are bands of cumulonimbus clouds ¡ª those that are rain-heavy, dense and towering ¡ª which can move slowly or stop, dumping their contents in one area.

Storms with these zones are difficult to predict, and over the past few years they have caused extensive damage, prompting the weather agency to make efforts to raise its forecasting accuracy.

Torrential rains in western Japan in 2018 and then in Kumamoto Prefecture in 2020, which caused the Kuma River to overflow its banks, resulted in catastrophic damage across the southwestern part of the country. Climate change could make these downpours even worse.

The agency used to issue warnings only when a linear precipitation zone was confirmed. But from this year, it will publish the information even when such an occurrence is merely predicted.

As a first step, the Meteorological Agency is set to begin forecasting possible linear rain belts from Wednesday. The country will be divided into 11 regions ¡ª including northern Kyushu, known for severe rainfall ¡ª and forecasts will be released from 12 to six hours in advance.

The researchers believe that such services will enable people to better plan for emergencies and evacuate faster. For example, if heavy rainfall is expected at night, advanced forecasting will enable residents in the designated areas to find shelter during the day.

In an announcement released in late April, the agency said that because of past struggles to provide accurate forecasts ahead of time, they will work together with industrial, academic and governmental organizations to expedite the development of better forecasting tools.

The agency has been collaborating with universities and other research institutions to develop the world¡¯s most advanced meteorological technology and ultimately improve the accuracy of forecasting precipitation at sea using a global navigation satellite system.

The agency said it will also conduct real-time simulation experiments using a numerical forecast model that is being developed based on calculations by the supercomputer Fugaku. Developed by Japan¡¯s state-funded research institute known as Riken, Fugaku is one of the world¡¯s fastest in terms of computing speed.

In cooperation with the science ministry, the agriculture ministry and Riken, the Meteorological Agency will use this year¡¯s rainy season to conduct intensive observations to better understand how linear precipitation zones work.

The agency plans to provide the same forecasting accuracy to individual municipalities in fiscal 2029.