Tropical storm Krosa, a Khmer word meaning crane, was swirling in the Pacific, south of Japan, and expected to make landfall near the city of Hiroshima from Wednesday, the weather agency said.

Though Krosa is unlikely to strengthen into a typhoon, its broad front meant it could affect a large swathe of Japan, dumping up to 1,000 mm (39 inches) in some parts of the west.

"A very large part of western and eastern Japan could face heavy rains, high winds and high tides," Ryuta Kurora, a spokesman for the Japan Meteorological Agency, told a news conference.

He urged authorities to review evacuation plans in areas that could be hit by the storm.

Krosa will arrive in the middle of Obon, the summer holiday season when many Japanese leave big cities for their ancestral hometowns to visit family graves.

Airlines and train operators warned that the storm could cause delays or cancellations, snarling travel just as many Japanese are returning to Tokyo and other cities.

"If I can't get back as planned, the impact on my job could be bad," one man told national broadcaster NHK.

More than 200 people died in torrential rains and flooding in parts of western Japan in 2018, areas that could also be hit by severe rains from Krosa.

REUTERS