The Japan Meteorological Agency's new disaster warning system, which was introduced Friday, will allow the agency to issue "emergency warnings" for any natural disasters on an unprecedented scale as a last resort to warn people of such calamities.
The introduction of the new emergency warning system was prompted by Typhoon No. 12 in 2011, which caused extensive damage on the Kii Peninsula and other areas. The village of Totsukawa in Nara Prefecture was ravaged by torrential rain from before dawn on Sept 2 and the agency alerted people by issuing a heavy rain warning shortly after 3.30am. The agency also issued a "sediment disaster," or landslide, alert in the early afternoon and a flood warning after 4pm.
However, heavy rain continued, causing large mudslides and rivers to rise. Six people died and six went missing.
An agency official expressed regret, saying, "If we had an emergency warning to issue, we could have better warned people." The agency had issued all the warnings related to heavy rain and had nothing to further warn people of the growing danger.
The agency issues various kinds of disaster management information such as those related to heavy rain that falls in a short period of time as well as flood forecasting, but lessons learned from Typhoon No. 12 convinced the agency that a new type of warning was necessary to alert people of large-scale natural disasters.
Mitsuhiko Hatori, director general of the agency, expressed his determination to minimise the number of people affected by natural disasters at a press conference Thursday. "We want to see zero victims of unprecedented natural disasters," he said.
Once every 50 years
The agency considers heavy rain and snow with a level of intensity observed only once every 50 years as the standard to issue an emergency warning. The agency said this standard was made by translating "a once-in-a-lifetime incident" into concrete numerical terms. The standard is based on past natural disasters that caused severe damage.
For heavy rain, the agency gauges rainfall in five square kilometre grids and issues an emergency warning if rainfall over 48 hours reaches the level of once every 50 years in 50 grids or more.
However, there were already four cases this summer for which the agency issued alerts, saying the cases would have been deemed serious enough to require an emergency warning. The agency issued a heavy rain alert in Yamaguchi and Shimane prefectures on July 28 and against torrential rain in Akita and Iwate prefectures on Aug 9. On Aug 24, the agency again issued a heavy rain alert in Shimane Prefecture. Hatori said, "It is quite rare for repeated instances of heavy rain to occur in such a short period of time."
Quick action important
The new emergency warning system has some problems.
For example, heavy rain in a localised area is excluded from emergency warnings because it falls in a small area for a short period of time.
On Aug 25, Osaka saw a record 27.5 millimetres of rain fall over a 10-minute period. Streets in downtown areas were flooded, but the incident would not have been subject to an emergency warning under its standards because the rain fell for a short period of time.
The agency considers the emergency warning as a last resort to warn people of danger and therefore it is difficult to decide the best time to issue it.
In the case of the heavy rain in Shimane Prefecture on July 28, when the agency issued an alert, saying the rain was equivalent to the level requiring an emergency warning, the rain had already passed its peak and some rivers had already flooded.
"Even if there is no emergency warning issued, it does not necessarily mean you are safe," an agency official said. The agency advises people to gather information from television or radio if unusual weather is expected and take action to protect themselves as quickly as possible in case of emergency.