The Japan Meteorological Agency (JMA) said the strong typhoon was moving northwest over the southern waters of Japan at a speed of 30 km/h.
On the morning of August 26, typhoon Shanshan had a central atmospheric pressure of 980 hectares, with the strongest wind near the center of the storm at 126 km/h, gusting up to 180 km/h.
The storm is expected to continue moving north and reach very strong intensity on August 27 before approaching the west and east of Japan.
The JMA's typhoon bulletin said that the sixth typhoon to form in the area around Japan this month could bring strong winds and severe weather as it approaches land, with winds approaching the center of the typhoon at 162km/h, gusting up to 216km/h.
The storm is expected to bring heavy rains to western and eastern Japan, mainly to areas along the Pacific coast, from August 27-28.
Tokai and Shikoku could see up to 200mm of rainfall in the 24 hours to the evening of August 27, while Kinki and southern Kyushu will see 150mm.
In the 24 hours to the evening of August 28, rainfall could reach 400mm in Tokai, 300mm in Kinki, Shikoku, southern Kyushu and 200mm in northern Kyushu.
The sea is expected to be rough with high waves on August 27.
Officials warn of extremely strong winds, landslides, floods in low-lying areas, rising water levels and river floods as well as high waves.
Japan Central Railway Company said it may cancel the Tokaido Shinkansen high-speed train service due to the storm.
Meanwhile, Enki Research weather experts said that when it makes landfall in Japan, Shanshan could cause severe damage of up to 10 billion USD due to gusts of wind, rising water and flooding.
The storm will bring water to wherever it strikes, but the main threat could be flooding across much of western Japan and the southern coast.
Shanshan could make landfall in Shikoku and then cross southern Honshu, causing $6-10 billion in damage, Chu Chu Watson, a disaster model maker at Enki Research, forecast on August 25.
Watson noted that if the storm sweeps through the Osaka-Kobe area, damage could reach $12-20 billion.
Typhoon Shanshan was originally a low pressure area near the Philippines, strengthening from August 22.
