Tropical Storm Dujuan is passing close to Japan and is forecast to rebuild into a typhoon by Tuesday morning, bringing powerful winds, exceptional rainfall and hazardous seas to the Izu Islands. Although its centre is expected to remain away from mainland Japan, evacuation warnings are already in place and flood, landslide and coastal alerts cover extensive areas. The storm’s approach comes as the Atlantic hurricane season remains conspicuously subdued and south-western Europe prepares for a late surge of September heat.
Dujuan expected to intensify after a brief lull
Dujuan briefly attained typhoon status on Friday before weakening back to a tropical storm on Sunday morning. Forecasters now expect the system to regain its former intensity by Tuesday morning, with sustained winds potentially reaching 80mph (129km/h) and gusts nearing 100mph.
Its projected route carries the storm across the Izu Islands before it continues north-eastwards. The main Japanese islands may avoid a direct strike, but an offshore track will offer little comfort to communities exposed to the storm’s outer bands, where wind and rainfall can remain severe.
After passing Japan, Dujuan is expected to lose organisation and dissipate over the north-west Pacific later this week. The timing of its re-intensification is particularly significant: conditions could deteriorate quickly as the storm approaches some of the country’s densely populated coastal and metropolitan regions.
Izu Islands face wind, flooding and landslide risks
Japanese authorities have issued evacuation warnings across the Izu Islands, where steep terrain and exposed coastlines heighten the danger. Widespread alerts cover intense rainfall, river and surface-water flooding, landslides and large waves. Residents in vulnerable locations face several hazards arriving together rather than sequentially.
The most serious concern is water. Along the southern coasts of the Chubu and Kanto regions, about 200mm (7.9in) of rain could fall within 24 hours. That is roughly equivalent to the average rainfall for the whole of September. In the Tokyo metropolitan area, some forecast models indicate that nearly 90mm could arrive within six hours on Monday evening. Further south, more than 80mm may fall across the Izu peninsula in just three hours, amounting to 38% of the month’s usual rainfall in a single evening. Such concentrated downpours can overwhelm drainage systems and trigger rapid changes in river levels.
Wind and sea conditions will compound the problem. Gusts approaching 10