In addition to earthquakes and volcanoes, Japan experiences many weather disasters. Knowledge about typhoons, torrential rain, heavy snow, extreme heat, and other hazards is essential for protecting lives.
Basic Knowledge
Main weather disasters:
① Typhoons and violent winds: Damage caused by strong winds, heavy rain, and storm surges.
② Torrential rain, floods, and sediment disasters: River flooding, debris flows, landslides, and slope collapses.
③ Heavy snow: Snow damage, avalanches, snow-removal accidents, and transportation disruptions.
④ Extreme heat and heatstroke: Occur frequently on extremely hot days of 35℃ or higher.
⑤ Tornadoes and downbursts: Localized strong winds that form from cumulonimbus clouds.
⑥ Drought: Little rain, affecting agriculture.
The Japan Meteorological Agency provides information in three levels: advisories, warnings, and emergency warnings. An emergency warning is issued when a serious disaster occurring once in several decades is expected. It is important to check local dangers in advance using a hazard map.
Advisory, warning, and emergency warning (three levels of weather information according to the expected degree of damage)
Hazard map (a disaster prediction map prepared and distributed by municipalities)
Heatstroke (a condition caused by the breakdown of body-temperature regulation in hot, humid conditions)
WBGT (heat index) (an indicator of heatstroke risk calculated from air temperature, humidity, and radiant heat)
Earthquake Early Warning (a warning issued after detecting P waves and before S waves arrive)
Evacuation information (five levels, alert levels 1–5; everyone should evacuate at level 4)
Further Study (Background and Significance)
During the July 2018 Western Japan floods, more than 200 people died, mainly in Hiroshima, Okayama, and Ehime Prefectures. Linear precipitation bands and sediment disasters occurred simultaneously in many places.
The Japan Meteorological Agency reports that the frequency of heavy rain is increasing due to global warming. Heavy rain of 50mm or more per hour has increased by about 1.5 times compared with the 1980s.
Among self-help, mutual help, and public help, the first priority during a disaster is self-help (protecting your own life). Advance preparation (stockpiling supplies, checking evacuation routes, and deciding how family members will contact one another) can determine whether people live or die. Cooperation among local residents (mutual help) and government action (public help) must be combined to build a disaster-resilient society.
Advances in meteorology, the spread of disaster-prevention education, and progress in technology (seismographs, Doppler radar, and satellites) have reduced the number of victims.
- Japan Meteorological Agency = advisory → warning → emergency warning
- Evacuation information = alert levels 1–5
- Level 4 = everyone evacuates; level 5 = a disaster has already occurred
- Check local dangers on a hazard map
- Self-help → mutual help → public help
- Stockpile water, food, and batteries for at least 3 days
- Use WBGT to assess heatstroke risk
Points of Caution (Easily Confused)
① The seriousness increases in the order of advisory → warning → emergency warning. ② Alert level 4 means that everyone should evacuate. At level 5, a disaster has already occurred, so take the best possible action to protect your life. ③ Evacuation advisories were abolished in 2021 and unified as “evacuation orders.” ④ Heatstroke can occur indoors as well (the problem is high temperature and humidity).
Practice
- What is the most serious information above a weather warning issued by the Japan Meteorological Agency?
- What is a map showing predicted disasters in a region called?
- What action should residents take at alert level 4?