Photo/Illutration Predicted path of Typhoon No. 10 as of noon on Sept. 4 (From the Japan Meteorological Agency’s website)

The Japan Meteorological Agency on Sept. 9 started a new forecast system of offering five-day predictions for the path and strength of tropical depressions that are likely to develop into typhoons.

The JMA, which had given only one-day predictions for such events, said it wants to provide residents, municipalities and other related authorities more time to prepare for typhoon-related disasters.

When maximum sustained winds of a tropical depression reach about 61.2 kph, it is considered to have developed into a typhoon.

The JMA then provides five-day forecasts of the typhoon’s direction and strength.

But when the system is still a tropical depression that might become a typhoon, only a 24-hour prediction was given due to the large margin of error in such forecasts.

The JMA said improvements in prediction technology have allowed it to expand such forecasts to five days.

Typhoon No. 15 that caused a widespread blackout, mainly in Chiba Prefecture, in September 2019 made landfall four days after a tropical depression grew into the typhoon. The JMA said it has since received many requests for earlier typhoon forecasts.

The JMA offers forecasts of typhoons and tropical depressions on its website: 
https://www.jma.go.jp/jp/typh/