As the death toll passes 100, we look at why the floods struck and if the forecast was accurate.

A typhoon and a stalled rain band combined to give Japan phenomenal amounts of rain, causing flooding and landslides that have killed more than 114 people.

The rain, however, started even before this, giving way to even more destruction.

On June 28, several days of heavy rain caused the Osaka River in central Honshu’s Gifu Prefecture to break through its embankment.

Mud hurtled down the hillside, making a major road impassable and leaving 81 local residents and hotel guests cut off.

Landslides were also reported in the city of Gero, where a concrete bridge was swept away.

Then, on July 3, Typhoon Prapiroon skirted the Kyushu island and grazed the north coast of Honshu.

The storm brought torrential downpours across many parts of Kyushu and Honshu, including the prefecture of Gifu where the ground was already saturated.

The risk of landslides and flash flooding was forecast in Gifu and neighbouring regions, but for many, the worst of the weather struck after the typhoon cleared away.

Trailing behind Typhoon Prapiroon was a line of clouds and rain that remained in place for three days. It is the length of time that the rain persisted over the region that triggered such a disaster.

As the typhoon moved away, the Japan Meteorological Agency issued an Emergency Warning for some of the provinces that were expected to be worst hit.

Emergency Warnings alert people to the significant likelihood of “catastrophes of extraordinary magnitude”.

Residents were advised to check for evacuation information from their local governments and move to safe places before conditions worsened.

As predicted, the rain was extremely heavy. According to the national broadcaster NHK, in 72 hours, 93 locations had set new rainfall records.

It would be unfair to say that this rain was poorly forecast. NHK reported the Emergency Warnings and the majority of people heard the alerts.

The problem in Japan is where to move people to. The country is mountainous and every year there is flash flooding from its seasonal ‘plum rains’ and/or typhoons.

Parts of Japan are also heavily populated. Some 5 million people were ordered to evacuate, but the order was not mandatory, so many people chose to ignore it.

As the death toll continues to rise, there will be questions over whether more should be done in the future when an alert of a “catastrophe of extraordinary magnitude” is issued.