Japan's Meteorological Agency issues an emergency warning when a typhoon is expected to approach an area with a central atmospheric pressure of 930 hectopascals or lower, or with maximum winds of up to 180 kilometers per hour.

This is an intensity that only occurs once every few decades.

The warning is for storm, storm surges or high waves.

Unlike a heavy rain emergency warning, the agency issues an emergency warning for an area about 12 hours before the center of the typhoon is forecast to arrive, before the situation has worsened.

The agency has only issued such a warning three times before. The latest warning is the fourth.