The government introduced a revamped weather warning system Thursday, ahead of the country＊s rainy and typhoon seasons.

The improved system, which features five alert levels for flooding, heavy rain, landslides and storm surges, was introduced by the Japan Meteorological Agency and the land ministry. The revamped system was put in place Thursday afternoon, with changes to the relevant laws taking effect on Friday.

An emergency warning will be issued when natural disasters may have already occurred, prompting municipalities to declare a Level 5 situation and issue orders urging residents to take emergency action to protect themselves.

A danger warning, which is a newly established category, will be announced for a Level 4 situation, and will prompt municipalities to instruct residents to evacuate.

A regular warning will be issued for a Level 3 situation, when an evacuation order for elderly and other vulnerable people will be announced.

An advisory will be issued for a Level 2 situation. An early warning or an alert over a possible disaster that may happen over the next five days will be announced for a Level 1 situation.

Flooding alerts will cover 400 large rivers across Japan.

Heavy rain alerts will cover the flooding of smaller rivers, while landslide alerts will warn people about landslides on steep slopes and debris flows.

Storm surges are defined as rises in seawater levels caused by a decrease in atmospheric pressure and tides crashing against coasts due to strong winds from typhoons and storms. They are not, however, tsunamis, which are triggered by earthquakes.

Such storm surges can result in a prolonged period of flooding in coastal areas, with high tides delivering further blows.

While the alerts will be based on tide levels, they will also reflect wave run-up heights in the future. Run-up height will first be reflected in alerts covering the city of Kurobe and the towns of Nyuzen and Asahi in Toyama Prefecture, which were hit especially hard by a tsunami in 2008, and will then be expanded to cover other areas of the country.

Disaster risk is heightened by a linear precipitation zone. In addition to its 12-hour forecast, the agency will also start providing two- to three-hour forecasts covering smaller areas.