The Japan Meteorological Agency issued a pre-emptive forecast warning that a line-shaped rain band could form in parts of Kochi and Tokushima prefectures [1].
These atmospheric patterns often trigger extreme rainfall, which significantly increases the risk of flash floods and landslides in mountainous or coastal regions. By issuing a forecast before the rain band fully materializes, officials aim to give residents critical time to move to safety.
The agency identified central and western Kochi Prefecture and northern Tokushima Prefecture as the primary areas of concern [1, 2]. According to the forecast, there is a high likelihood that the rain band will develop within three hours [1]. The expected occurrence period is slated for the late night of the 17th [2].
Warm, moist air is fueling the current weather system, raising the risk of extremely heavy precipitation. The agency urged residents to take immediate protective action before the rain begins in earnest to avoid being trapped by rising waters.
"It is dangerous to evacuate outdoors after a linear precipitation zone has already developed," the Japan Meteorological Agency said [2].
Local authorities are monitoring the situation as the time window for the formation of the rain band closes. The agency emphasized the need for urgency in the face of potential disasters. "We want people to take appropriate disaster prevention actions promptly," the agency said [1].
“It is dangerous to evacuate outdoors after a linear precipitation zone has already developed”
The use of pre-emptive forecasts represents a shift toward proactive disaster mitigation in Japan. By narrowing the warning window to three hours, the Japan Meteorological Agency attempts to reduce the 'evacuation gap'—the time between a warning and the onset of dangerous weather—thereby potentially reducing casualties associated with the sudden onset of linear precipitation zones.
