Heavy Rain and Typhoons In Japan

Japanese Typhoons

Typhoons are persistent heavy rains accompanied by strong winds. Rainstorms can disrupt travel schedules by shutting down public transport and making it impossible to walk outside. They can also create lasting damage to urban infrastructure. In areas with insufficient countermeasures, flooding can damage interiors of buildings while winds blow away certain objects. Confirm the locations of nearby designated evacuation areas to avoid being injured by flooded electrical systems or being hit by flying objects. Low-pressure systems formed above tropical waters are known as tropical low-pressure systems. Those that exist in northwest Pacific (north of the equator and west of 180 E) or the South China Sea and has an average 10-minute maximum speed of at least 17m/s (or 34 knots, wind force of 8 on the Beaufort scale) are known as typhoons.

2. Warnings and Advisory Information

The Japan Meteorological Agency issues various alerts about incoming rainstorms and typhoons based on their intensity and geographical information. Ranging in magnitude from relatively weak advisories to more urgent warnings and emergency warnings, these alerts are relayed by TV stations and over the web by media outlets such as the NHK. In the below table, we have summarized the content and definition of different alerts.

Categories and Definitions of Special Alerts regarding Heavy Rains and Typhoons from Japan Meteorological Agency

Heavy rain advisory: Issued when it is forecasted that heavy rain will cause landslides or flooding. This advisory will continue even after the rain has stopped if there is still the risk of landslides and other disasters.

Heavy rain warning: Issued when it is forecasted that heavy rain will cause major landslides or flooding. To clarify the risks to be noted, the issuance will be “Heavy rain warning (Landslides), Heavy rain warning (Flooding), or Heavy rain warning (Landslides, Flooding). This warning will continue even after the rain has stopped if there is still the risk of major landslides and other disasters.

Heavy rain emergency warning: Issued when heavy rain of an intensity seen only once every few decades is forecasted due to typhoons or concentrated rainfall, or when a typhoon with an intensity observed only once every few decades or heavy rain from a comparable tropical low-pressure system is forecasted. When issued, it is forecasted that there is an extremely high risk of major landslides or flooding. This emergency warning will continue even after the rain has stopped if there is still a serious risk of major landslides and other disasters.

Flood advisory: Issued when it is forecasted that heavy rain or snowmelt upstream can cause a significant increase in water volume downstream that risk flooding. Possible impact from flooding includes rivers and streams increasing in volume, as well as damaging of levees.

Flood warning: Issued when it is forecasted that heavy rain or snowmelt upstream can cause a significant increase in water volumes downstream that risk serious flooding. Possible impacts from flooding include rivers and streams increasing in volume or overflowing, as well as damaging and breaking of levees.

High wave advisory: Issued when there is the risk of disasters, including accidents and damage to coastal facilities due to high waves.

High wave warning: Issued when there is the risk of serious disasters, including accidents and damage to coastal facilities due to high waves.

High wave emergency advisory: Issued when it is forecasted that high waves will be produced by a typhoon with an intensity observed only once every few decades, or from heavy rain from a comparable tropical low-pressure system.

Storm surge advisory: Issued when there is the risk of disasters occurring through the abnormal rise of the ocean surface due to typhoons and low-pressure systems.

Storm surge warning: Issued when there is the risk of serious disasters occurring through the abnormal rise of the ocean surface due to typhoons and low-pressure systems.

Storm surge emergency warning: Issued when it is forecasted that storm surge will be produced by a typhoon with an intensity observed only once every few decades or heavy rain from a comparable tropical low-pressure system.

Gale advisory: Issued when there is the risk of disasters occurring from strong winds.

Storm warning: Issued when there is the risk of serious disasters occurring from strong winds.

Storm emergency warning: Issued when it is forecasted that storm will be produced by a typhoon with an intensity observed only once every few decades or heavy rain from a comparable tropical low-pressure system.

Thunderstorm warning: Issued when there is the risk of disasters occurring from extreme weather patterns such as lightning, hail, heavy rains, or sudden gusts of wind.

Source: “Type and content of different meteorological warnings,” homepage of the Japan Meteorological Agency: https://www.jma.go.jp/jma/kishou/know/bosai/warning_kind.html

3. Countermeasures

Collect Relevant Information

First, it is important to gather relevant information. You should pay attention to weather information about heavy rains and typhoons broadcasted on radio, TV, and over the Internet. Minimize outside activities that are not absolutely necessary. Return your place of accommodation immediately in preparation for an emergency. Do not go near overflowing streams, gutters, and base of slopes. When the risk of disaster increases, specific instructions will be given by municipal authorities through various means and loudspeaker-mounted vehicles. Follow those instructions whenever possible.

Evacuation

Even if no specific instructions for evacuations are given, different physical conditions mean that some accommodations can already be in danger. Evacuate as soon as you sense danger. In particular, children, the elderly, and those with physical handicaps should be evacuated in advance.

If you happen to be outside when a typhoon approaches, move immediately to a nearby building and remain there until the typhoon subsides. Either way, do not go out to repair windows or roofs while the winds are still raging.

Water at the knee-deep level makes walking difficult. In cases of heavy rain, make sure to evacuate to higher ground before the water level reaches knee-deep. If the water is moving rapidly, evacuate immediately, as the speed of moving water makes moving much more difficult. For those in underground areas, move immediately above-ground to a designated evacuation area, or a sturdy nearby building, preferably at least two stories high.

During evacuations, one should wear shoes, such as sneakers with shoelaces, that are difficult to take off and easy to walk in. Shoes that are easily taken off, such as long boots, are not recommended. While walking in areas overflowing with water, one should be mindful of potential dangers beneath the water. Use a long stick to check for safety beneath the water before walking into the water. In areas where water is flowing rapidly, groups of people should try themselves together to prevent separation.

After returning to the place of accommodation, one should check the safety of the building. In particular, check if there are damages to electrical lines, and report immediately to local utility companies and other neighbors should there be any damages. Wait for professionals to show up to repair the damages. Do not attempt to repair the damages without professional assistance.

Source: “Actions to be Taken in Response to Dangers from Wind- and Water-Caused Disasters,” e-College (Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications)
http://open.fdma.go.jp/e-college/study00/kiso/saigai_chishiki/fuuzuigai/04/index.html

Reference: page 149, “Disaster Preparedness Tokyo,” Tokyo Metropolitan Government

Source: Fire and Disaster Management Agency of the Ministry of Internal Affairs and Communications