Safety and Disaster Prevention: Typhoons and Heavy Rain
Typhoon
The areas of low pressure that occur over tropical seas are called tropical cyclones, and a tropical cyclone that is in a low pressure area in the northwest Pacific or South China Sea and whose maximum wind velocity is equal to or greater than 17 m/second (category 8) is called a typhoon.
Heavy Rain
Characteristics of Heavy Rain
Natural disasters that occur with the rainy season and typhoons exert a great influence on the lives and property of the people and occur every year in Japan. On occasion, the amount of rainfall in one day can be the usual amount for one month. In such cases, river flooding, landslides, etc. occur, and the lives of residents are endangered. Flood warnings and heavy rain warnings are issued, so it is important that one pays attention to the weather information.
Rain patterns in relation to natural disasters
Simple classification of rain patterns
- Short, heavy spans of rain (1 to 2 hours)
- Long periods of rain
- Long periods, with heavy spells
The third pattern of rainfall has almost always been responsible for natural disasters.
The criterion for a natural disaster occurrence is said to be when the amount of rainfall for one day corresponds to about one-twentieth the average yearly precipitation (Kyoto: 1,581 mm).
Heavy Rain from Typhoons
When a typhoon is approaching Japan and there is a seasonal or autumnal stationary rain front in home waters, heavy rainfall may occur even if the typhoon remains relatively far away. In this case, the rain will often continue for a long period, and when the typhoon crosses over Japan, heavier rain and a larger natural disaster may occur.