Glossary
Weather warnings/advisories
Thunder
- Thunderstorm advisory
- The Japan Metrological Agency issues it when it forecasts that disaster due to lightning strikes is expected to occur.
- In addition to lightning strikes, alerts may be added to warn of the possibility of damage to people and buildings due to violent weather phenomena occurring often under developing cumulonimbus clouds, such as sudden heavy rain, gusty winds such as tornadoes, and hail.
- A thunderstorm advisory also includes an alert for sudden and strong rain.
Heavy Rain
- Level 2 Advisory (Heavy Rain)
- Issued when there is a risk that disasters may occur due to rising river water levels. It is issued when the basin rainfall index has reached, or is forecast to reach within the next three hours, the Level 2 Advisory (Heavy Rain) criteria in one or more sections.
- It is also issued when waterways, sewer systems, etc. may overflow due to short-duration localized heavy rain and disasters may occur, when the surface rainfall index has reached, or is forecast to reach within the next hour, the Level 2 Advisory (Heavy Rain) criteria.
- Level 3 Warning (Heavy Rain)
- Issued when there is a risk of serious disasters due to rising river water levels. It is issued when any section reaches, or is forecast to reach within the next three hours, the Level 3 Warning (Heavy Rain) criteria for the basin rainfall index.
- It is also issued when waterways, sewer systems, etc. may overflow due to short-duration localized heavy rain and serious disasters may occur, when the surface rainfall index has reached, or is forecast to reach within the next hour, the Level 3 Warning (Heavy Rain) criteria.
- Level 4 Urgent Warning (Heavy Rain)
- Issued when there is a high risk of serious disasters due to rising river water levels. It is issued when multiple sections have reached, or are forecast to reach within the next three hours, the Level 4 Urgent Warning criteria for the basin rainfall index.
- It is also issued when waterways, sewer systems, etc. may overflow due to short-duration localized heavy rain and the risk of serious disasters is high, when the surface rainfall index has reached, or is forecast to reach within the next hour, the Level 4 Urgent Warning (Heavy Rain) criteria.
- Level 5 Emergency Warning (Heavy Rain)
- Issued when the risk of serious disasters due to heavy rain is extremely high.
River flooding
- Level 2 Flood Advisory
- Issued when a river rises to the flood advisory water level and the water level is expected to rise further； when conditions at or above the flood advisory water level and below the evacuation decision water level are continuing；
- or when the evacuation decision water level has been reached but the water level is not expected to rise further.
- Level 3 Flood Warning
- Issued when a river is expected to reach the flood danger water level due to rising water； when it has reached the evacuation decision water level and the water level is expected to rise further；
- when the water level drops below the flood danger water level while flood danger information is in effect, except when it has dropped below the evacuation decision water level；
- or when conditions exceeding the evacuation decision water level continue, except when there is no longer a possibility of the water level rising.
- Level 4 Urgent Warning (Flooding)
- Issued when, due to rising river water levels, a rapid rise is expected to soon exceed the flood danger water level and the water level is expected to rise further； when the flood danger water level has been reached； or when conditions exceeding the flood danger water level continue.
- Level 5 Emergency Warning (Flooding)
- Issued when flooding has occurred or is imminent.
Landslide
- Level 2 Advisory (Landslide)
- Issued to advise people when there is a possibility of landslides due to heavy rain.
- Level 3 Warning (Landslide)
- Issued to warn people when there is a possibility of serious landslide disasters due to heavy rain.
- Level 4 Urgent Warning (Landslide)
- Issued to warn people when there is a high possibility of serious landslide disasters due to heavy rain.
- Level 5 Emergency Warning (Landslide)
- Issued when there is an extremely high possibility of serious landslide disasters due to heavy rain.
Storm surge
- Level 2 Advisory (Storm Surge)
- Issued by about 18 hours before the tide level, or for storm surge forecast coasts the water level including the effect of wave run-up, is forecast to reach the criteria for Level 4 Urgent Warning (Storm Surge).
- Level 3 Warning (Storm Surge)
- Issued by about 12 hours before the tide level, or for storm surge forecast coasts the water level including the effect of wave run-up, is forecast to reach the criteria for Level 4 Urgent Warning (Storm Surge).
- Level 4 Urgent Warning (Storm Surge)
- Issued when there is a risk of serious disasters due to storm surge. It is issued by about 6 hours before the tide level, or for storm surge forecast coasts the water level including the effect of wave run-up, is expected to reach the criteria for Level 4 Urgent Warning (Storm Surge).
- Level 5 Emergency Warning (Storm Surge)
- For storm surge forecast coasts, issued when either the observed value or the latest forecast of the tide level,
- or the water level including the effect of wave run-up, exceeds the criteria and the situation is forecast to continue for a certain period, or when a levee breach or flooding of the hinterland has actually been confirmed.
- For areas other than storm surge forecast coasts, issued when the observed value or latest forecast of the tide level exceeds the criteria and the situation is forecast to continue for a certain period.
Tsunami
- Tsunami advisory
- Tsunami advisory is issued when there is a risk of disaster due to a tsunami with a maximum forecast height of between 0.2 meter and 1 meter.
- Persons in the sea must immediately get out of the water and distance themselves from the coastline. Do not go swimming or rock fishing as it is dangerous. Do not enter the sea or go near the coastline until the advisory is lifted.
- Tsunami warning
- Tsunami warning is issued when there is a risk of disaster due to a tsunami with a maximum forecast height of between 1 meter and 3 meters.
- Persons in coastal areas and along rivers must immediately evacuate to higher ground, buildings designated as tsunami evacuation faciities, or other safe locations. Do not leave your safe location until the warning is lifted.
- Great tsunami warning
- Great tsunami warning is issued when there is a risk of disaster due to a tsunami with a maximum forecast height of over 3 meters.
- Persons in coastal areas and along rivers must immediately evacuate to higher ground, buildings designated as tsunami evacuation faciities, or other safe locations.
- Do not leave your safe location until the warning is lifted.
Emergency warning
- Emergency warning
- A warning issued by a meteorological observatory to warn that the risk of a serious disaster is extremely high. There are Emergency Warnings for weather, landslides, tsunamis, storm surges, and high waves.
- Weather Emergency Warnings include Emergency Warnings for storm, storm snow, heavy rain, and heavy snow. The tsunami Emergency Warning is issued as a Major Tsunami Warning.
- Level 5 Emergency Warning (Heavy Rain)
- Issued when the risk of serious disasters due to heavy rain is extremely high.
- Level 5 Emergency Warning (Flooding)
- Issued when flooding has occurred or is imminent.
- Level 5 Emergency Warning (Landslide)
- Issued when there is an extremely high possibility of serious landslide disasters due to heavy rain.
- Heavy snow emergency warning
- Heavy snow emergency warning is issued when heavy snow causing the amount of snowfall once in every several decades is expected.
- Storm emergency warning
- Storm emergency warning is issued when stormy weather is expected due to as a strong typhoon or an extratropical cyclone as it occurs once in every several decades.
- Blizzard emergency warning
- Blizzard emergency warning is issued when stormy weather with snow is expected due to as a strong typhoon or an extratropical cyclone as it occurs once in every several decades.
- Vigilance is called for when “major disaster due to obstruction to visibility (shutting out the view) with snow etc.”
- in addition to “major disaster due to storm” are highly expected.
- Level 5 Emergency Warning (Storm Surge)
- For storm surge forecast coasts, issued when either the observed value or the latest forecast of the tide level,
- or the water level including the effect of wave run-up, exceeds the criteria and the situation is forecast to continue for a certain period, or when a levee breach or flooding of the hinterland has actually been confirmed.
- For areas other than storm surge forecast coasts, issued when the observed value or latest forecast of the tide level exceeds the criteria and the situation is forecast to continue for a certain period.
- High waves emergency warning
- High wave emergency warning is issued when high wave is expected due to as a strong typhoon or an extratropical cyclone as it occurs once in every several decades.
- This “high wave” is totally different from “tsunami” due to earthquake.
Weather Disaster Prevention Bulletin / Weather Commentary Information
- Weather Disaster Prevention Flash Report (Record-breaking Short-term Heavy Rainfall)
- Information issued when short-duration heavy rainfall of a kind that occurs only about once every few years is observed by ground rain gauges or analyzed using a combination of weather radar and ground rain gauges.
- Weather Disaster Prevention Flash Report (Occurrence of a Linear Rainband)
- Information explaining, using the keyword “linear rainband,” a situation in which very heavy rain continues to fall over the same area due to a band-shaped precipitation zone while the risk of disasters caused by heavy rain is rapidly increasing.
- Weather Disaster Prevention Flash Report (Advance Forecast of a Linear Rainband)
- Issued when the possibility of a linear rainband occurring within the next three hours has increased.
- Weather Disaster Prevention Flash Report (Tornado Advisory/Tornado Sighting)
- Issued for affected primary subdivisions, such as the southern part of a prefecture, when meteorological conditions are judged to be favorable for severe gusts caused by tornadoes, downbursts, etc. occurring under cumulonimbus clouds.
- The valid period is one hour from the time of issuance.
- Meteorological Commentary Information (Half-day-ahead Forecast of a Linear Rainband)
- Issued roughly half a day in advance when the possibility of heavy rain caused by a linear rainband is expected to be relatively high, with the aim of encouraging people to raise their level of preparedness for heavy rain.
- *the website of the Japan Meteorological Agency「kikikuru(Warning risk distribution)」
Sediment disaster warning services
- Sediment disaster warning services
- This information identifies the relevant municipalities and calls for vigilance against landslides, in order to support mayors’ decisions to issue evacuation orders and residents’ decisions on voluntary evacuation.
- It is jointly issued by Hiroshima Prefecture and the Hiroshima Local Meteorological Office. From May 2026, notifications and related communications will be made under the name
- “Level 4 Urgent Warning (Landslide)” together with warnings related to landslides under Article 13, Paragraph 1 of the Meteorological Service Act.
- Index of rainfall in the soil
- The soil water index is an index used to determine the increase in landslide risk caused by rainfall.
- Landslides associated with heavy rain, such as slope failures and debris flows, are closely related not only to the rain currently falling but also to the amount of water in the soil from rain that has already fallen.
- The soil water index numerically represents, using a tank model, how much rainwater has accumulated in the soil as water content. It is used as a criterion for deciding whether to issue warnings and other information related to landslides.
- Information on risk of landslide disasters
- In Hiroshima Pref, it provides the detailed information regarding a degree of risk of occurring sediment disaster in regions in 5km mesh supplementing the contents of sediment disaster alerting information.
- The city will issue evacuation instructions for people in the landslide warning area according to the risk level of the indicated area.
Flood forecast on designated rivers
- Flood forecast on designated rivers
- The Japan Meteorological Agency jointly with Ministry of Land, Infrastructure, Transport and Tourism or prefectural agencies gives forecasts of floods with the water level or the volume of flowing water
- regarding the designated rivers for reference of determination of prevention activities against flood or raised water level in the river, or act of resident’s evacuation.
- In Hiroshima city, the following rivers are designated in advance.
- The river forecasting floods) The section managed by the nation of upstream of Ootagawa River, downstream of Ootagawa River, Misasagawa River and Nenotanigawa River
Information on reaching water level
- Information on reaching water level
- When the water level reaches a certain level in a river that has been designated as a river requiring notification and dissemination of information regarding the reaching of flood danger water level,
- the river administrator (Ministry of Land, Infrastructure, Transport and Tourism or the prefectural government) will announce the information about the reaching of such level.
- The following rivers in Hiroshima have already been designated as requiring notification. River publicizing a water level
- The river managed by the nation : Kyuootagawa River, Motoyasugawa River, Furukawa River
- The river managed by the prefecture : Yahatagawa River, Yasukawa River, Misasagawa River, Nenotanigawa River, Minochigawa River, Senogawa River, Fuchuookawa River, Suzuharigawa River, Okanoshitagawa River, Nabaragawa River
- Level 2 Information to call attention to flooding
- Overflow advisory information is issued when the water level of water level observatory to be criteria reaches an overflow advisory water level in the river publicizing a water level.
- Level 3 Information to provide a warning on flooding
- Overflow alerting information is issued when the water level of water level observatory to be criteria reaches a level of determing the evacuation in the river publicizing a water level.
- Level 4 Information on potential flood hazards
- Overflow danger information is issued when the water level of water level observatory to be criteria reaches an overflow danger water level in the river publicizing a water level.
- Level 5 Information on flooding
- Issued when flooding has occurred or is imminent.
Typhoon information
- Typhoon information
- Issued when a typhoon forms. It includes current observations and forecasts of the typhoon’s position, intensity, and other details. As the typhoon approaches Japan, more detailed information is provided with more frequent updates.
Earthquake information
- Seismic intensity
- The seismic intensity is a scale to measure the intensity of earthquakes.
- The Japan Meteorological Agency seismic intensity (shindo) scale gives a total of 10 levels of
- earthquake: “shindo 0”, “shindo 1”, “shindo 2”, “shindo 3”, “shindo 4”, “shindo 5-lower”, “shindo 5-upper”, “shindo 6-lower”, “shindo 6-upper”, “shindo 7”.
- You can confirm effects on people, indoor situations and outdoor situations in each seismic intensity (shindo) scale on the website of The Japan Meteorological Agency.
- *The website of The Japan Meteorological Agency “Seismic intensity (shindo) scale explanation table of The Japan Meteorological Agency”
- （http://www.jma.go.jp/jma/kishou/know/shindo/kaisetsu.html）
Observed information
Information on amount of rainfall
- Rainfall in 10 minutes
- It is rainfall in the most recent 10 minutes.
- Rainfall in 60 minutes
- It is rainfall in the most recent 60 minutes (1 hour). You can confirm the strength of rain and the way rain falls on the website of The Japan Meteorological Agency.
- *The website of The Japan Meteorological Agency “The strength of rain and the way rain falls”
- http://www.jma.go.jp/jma/kishou/know/yougo_hp/amehyo.html
- Effective rainfall
- Effective rainfall is the standard rainfall calculating the effect of rainfall in the past by decreasing it over time. This city’s system uses the 72 hours half-value period.
- Cumulative rainfall
- “Cumulative rainfall” is a total amount of rainfall from starting raining to that time. Cumulative rainfall will be reset after no rain continues for a certain period of time. When a rainfall is detected after that, it is regarded as new rain (starting raining).
State of rain clouds
- High-resolution Precipitation Nowcasts
- High-resolution Precipitation Nowcasts provide short-range precipitation intensity predictions with a spatial resolution of 250 m. They are derived from weather radar data by The Japan Meteorological Agency.
Standard water level
- Stand-by water level for flood fighting corps
- It is a water level set to flood prevention warning rivers and it is also the standard water level which flood prevention teams standby against floods and storm surges and prepare for flood prevention activities.
- It corresponds to a water level of notify, written in the provisions of Article 12 of the Flood Prevention Act. The flood control warning rivers of this city are as follows.
- The flood control warning river)
- The river managed by the nation: Ootagawa River, Misasagawa River, Nenotanigawa River, Kyuootagawa River, Motoyasugawa River, Tenmagawa River
- The river managed by the prefecture : Yahatagawa River, Yasukawa River, Misasagawa River, Nenotanigawa River, Minochigawa River, Senogawa River, Enkougawa River, Kyoubashigawa River
- Flood watch water level
- It is a water level to be cautious about disaster occurrence due to floods and storm surges (warning water level given by the provisions of Article 12 of the Flood Prevention Act).
- Also, it is the standard water level which flood prevention teams etc. dispatch in the flood prevention warning rivers.
- It is essential that we pay fully attention to rise of a water level after reaching.
- Water Level Basis for Decision to Evacuate
- This is the water level at which the mayor of the municipality will make a decision to issue evacuation instructions for the elderly and other persons requiring special care, and begin alerting residents to information about flooding.
- After it has been reached, sufficient caution is required regarding rising water levels.
- Flood danger water level
- This is a water level that requires special warning about the occurrence of disasters due to flooding (Emergency warning water level set forth in Article 13 of the Flood Control Act),
- and it serves as a guide for the mayor of the municipality to issue evacuation instructions, etc., and as a reference for residents to make evacuation decisions.
- After it has been reached, extreme caution is required regarding rising water levels.
- Overflow start level
- This is the water level at each point where overflow starts, such as the top of an embankment (or the height of the ground behind the embankment), in a series of areas of a river
- that are considered to have a high possibility of overflowing or flooding, converted into the water level at the water level observatory that serves the area.
Tide level information
- Warning tide level
- It is the standard tide level which flood prevention teams standby against storm surges and prepare for flood prevention activities. It has been set T.P.2.1m in Hiroshima port designated for Hiroshima city.
- Tide Level Alert
- It is a tide level to be cautious about disaster occurrence due to storm surges while it is the standard tide level which flood prevention teams etc. dispatch. It has been set T.P.2.5m in Hiroshima port designated for Hiroshima city.
- Astronomical tide
- Such as high tide, low tide and flood tide, neap tide, a change in tide level caused by tidal force of moon and sun is called “astronomical tide” and its tide level is called “astronomical tide level”.
- If there is an observation data with good accuracy about a certain point in long term, astronomical tide level of that point can be predicted in a high accuracy.
Evacuation information
Alert (call for voluntary evacuation)
- Alert (call for voluntary evacuation)
- Disaster prevention information (such as weather information) is transmitted to the entire city or areas where required when a disaster is deemed likely to occur such as when a Level 3 Warning (Heavy Rain) or similar is issued to alert the resident and, depending on the conditions,
- the city will check dangers in the area and encourage residents to evacuate (voluntary evacuation) if judged to be dangerous.
[Alert Level 3] Evacuation of the elderly, etc.
- [Alert Level 3] Evacuation of the elderly, etc.
- The city will issue this instruction when there is a possibility of a disaster occurring.
- This city generally issues it for residents living in dangerous areas such as sediment disaster special alert and flood-assumed areas in elementary school districts.
- The actions required of residents are as follows.
- Persons requiring time to evacuate, such as the elderly, the disabled, and those with small children, and persons who assist them must immediately start evacuation activities at designated emergency evacuation areas set up by the city, or at the homes of relatives or friends in safe locations.
- It is desirable for people other than those indicated above to suspend their normal activities, such as refraining from going outside, to work and similar activities, and to prepare for evacuation or evacuate voluntarily if necessary.
[Alert Level 4] Evacuation order
- [Alert Level 4] Evacuation order
- The city will issue this order when there is a increased possibility of a disaster.
- This city generally issues it for residents living in dangerous areas such as sediment disaster special alert and flood-assumed areas in elementary school district.
- The actions required of residents are as follows.
- Evacuate immediately from at-risk areas.
- For floods, storm surges, and inland flooding, if hazard maps or other sources confirm that safety can be secured indoors, such as on an upper floor, it is also possible to secure safety indoors at your own discretion.However, for landslides and tsunamis, evacuation to another location is necessary.
[Alert Level 5] Ensure emergency safety
- [Alert Level 5] Ensure emergency safety
- It is issued by the city in situations where a disaster has occurred or is imminent, or where it is actually considered dangerous to evacuate in order to ensure personal safety.
- The actions required of residents are as follows.
- Due to the danger to life, take action to ensure safety immediately.
- If evacuating to a designated emergency evacuation area or similar location is dangerous, you should immediately ensure your own safety by moving to a higher location, or a place away from mountains or cliffs that you can judge to be relatively safe.
Dangerous areas
Flood-assumed area
- Flood-assumed area
- Regarding the river forecasting floods and the river designated the river publicizing a water level,
- Ministry of Land, Infrastructure, Transport and Tourism and prefectures designates the areas assumed to flood when the said rivers
- overflow due to assumed maximum rainfall as a flood-assumed area in order to reduce flood damages through securing smooth and prompt evacuation in case of flood or preventing floods.
- Also, they publicize designated areas and assumed water depth and duration time of flooding in case of flood as a flood-assumed area chart.
- You find a list of target rivers and setting of rainfall on this city’s website.
- *This city’s website “Flood hazard map in Hiroshima city”
- （https://www.city.hiroshima.lg.jp/site/saigaiinfo/17890.html）
Possible sediment disaster areas
- landslide disaster warning area
- These areas are designated by Hiroshima Prefecture in accordance with the Landslide Disaster Prevention Law, which was enacted in response to the landslide that occurred in Hiroshima City and other areas on June 29, 1999.
- These areas are deemed to pose a risk to the lives or bodies of residents in the event of a collapse of steep slopes.
- Special alert area for soil and sand disaster
- These areas are designated by Hiroshima Prefecture based on the Landslide Disaster Prevention Law, and are recognized as areas where the collapse of steep slopes, etc.
- could cause damage to buildings and significant harm to the lives or bodies of residents, etc.
- Permission is required for certain development activities, and structural regulations for buildings are enforced.
Expected inundation area due to rainwater flooding
- Estimate inland waters flooding area
- This city publishes areas expected to be inundated by inland flooding under the assumed maximum-scale rainfall based on the Flood Control Act.
- *Hiroshima City website ”Flooding (by Inland Waters) Hazard Map”.
- https://www.city.hiroshima.lg.jp/living/suido-gesuido/1005966/1026319/1026321/1003118.html
Estimated storm surge and flood area
- Estimated storm surge and flood area
- Hiroshima Prefecture has published an estimated storm surge and flood area map showing the estimated areas and depths of flooding in the event of a typhoon storm surge.
- There are currently three possible cases of a maximum scale case, a 30-year probability case, and an Isewan Typhoon scale case.
- The estimated storm surge and flood area map can be viewed at the website of Hiroshima Prefecture.
- * Hiroshima Prefecture website ”Portal Site Hiroshima for disaster of storm surge and tsunami”
- https://www.takashio.pref.hiroshima.lg.jp/portal/top.aspx
Tsunami disaster special alert area
- Tsunami disaster special alert area
- Hiroshima Prefecture designates areas where evacuation systems need to be maintained to prevent tsunami disasters as tsunami disaster special alert areas so that residents of areas where there is a risk of lost lives or injuries in the event of a maximum class tsunami are ”notified”
- regarding tsunami flood estimates and reference water levels, and so that residents can ”escape” from a tsunami smoothly and quickly in times of emergency.
- The estimated tsunami disaster special alert area map can be viewed on the website of Hiroshima Prefecture.
- *Hiroshima Prefecture website ”Portal Site Hiroshima for disaster of storm surge and tsunami”
- https://www.takashio.pref.hiroshima.lg.jp/portal/top.aspx
Evacuation area etc.
Designated emergency evacuation area
- Designated emergency evacuation area
- Those are facility and place designated by this city in advance in classification of disaster as an evacuation area in order to protect people’s life from imminent danger of disaster. These are the evacuation sites will be established when evacuation instructions are issued.
- City-owned facilities such as school or community center are mainly designated. Types of disaster: landslides, floods, storm surges, inland flooding, earthquakes, tsunamis, and large-scale fires
Designated shelter
- Designated shelter
- These are facilities designated by Hiroshima City in advance as a location for residents to live temporarily for a certain period if they have become homeless due to disaster.
- Some facilities also serve as designated emergency evacuation areas.
- Schools, sports centers and similar facilities are mainly designated.
Others
Civil protection services
- Civil protection services
- We will inform you of any information on civil protection announced by the national government (information on ballistic missiles, guerilla attacks, air strikes, large-scale acts of terrorism, and other relevant information on civil protection).
Headquarter for disaster control
- Headquarter for disaster control
- It is established in order to respond to a possible large-scale disaster. A mayor and a ward mayor play a role as a chief of the headquarter in the city and in the ward respectively.
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