Dujuan Is Skirting Japan — Why Rain Is the Main Threat
Tropical Storm Dujuan was skirting Japan's Pacific coast on 21 September 2026 without making a direct mainland landfall, while bringing heavy rain to the Izu Islands and the Kanto region.
The system briefly reached typhoon status, a stronger stage of the same kind of storm, on Friday 18 September before weakening back to tropical storm strength on the morning of Sunday 20 September, according to the latest assessment. It was expected to restrengthen to typhoon intensity again by Tuesday morning 22 September, with forecast sustained winds of 80mph (129km/h) and gusts approaching 100mph. The Guardian
Japan Meteorological Agency analyses tracked that fluctuation closely. The Agency designated the system as T2625 (DUJUAN). At 06:00 on 17 September it was recorded as a Large Tropical Storm with central pressure of 996 hPa, a measure where lower numbers mean a stronger storm, and winds of 20 m/s (40 kt). In its bulletin issued at 12:45 UTC on 19 September, the RSMC Tokyo-Typhoon Center, the regional office in Tokyo that tracks typhoons, analyzed Dujuan at 12:00 UTC as grade TY, Large scale, centered at 27.9N 138.4E. By 15:00 JST on 20 September, JMA analyzed it as a Large Typhoon, forecasting a position at 31.2N 137.5E at 03:00 JST on 21 September.
The track took the center across the Izu Islands, where evacuation warnings were in place on 21 September. An emergency warning had been issued for Oshima Town in the Izu Islands, Tokyo Prefecture, with officials urging residents to evacuate to safer locations. NHK World Heavy rain affected both the Izu Islands and Kanto on 21 September. The Japan Times
Forecasters pointed to rainfall, not wind, as the immediate hazard. About 200mm of rain was forecast along the southern coasts of the Chubu and Kanto regions in 24 hours, roughly equivalent to average rainfall for the entire month of September. Models suggested nearly 90mm could fall in the Tokyo metropolitan area within six hours on the evening of Monday 21 September. The Izu peninsula could receive more than 80mm in three hours, or 38% of the month's usual rainfall. The Guardian
That evolution followed earlier guidance. On 17 September, Dujuan was expected to develop into a large-scale severe tropical storm and was forecast to potentially affect Japan over the Silver Week holidays, a cluster of September public holidays. The subsequent forecast kept the center offshore of mainland Honshu while maintaining a north-eastward motion, with dissipation in the north-west Pacific later in the week.
That western Pacific activity contrasted with an unusually quiet Atlantic. Tropical Storm Fay developed south-west of the Azores over the weekend of 19-20 September. It was not expected to strengthen further, extending the record for the latest first hurricane to form in a season during the satellite era. The previous mark for latest first hurricane formation was 11 September, set in 2002 by Hurricane Gustav and equalled in 2013 by Hurricane Humberto.
The broader context here is operational rather than categorical. A skirting track with no mainland landfall can still produce mainland-scale disruption when forward speed, moist air and coastal hills concentrate rain over short periods. Hourly rates near 80-90mm overwhelm urban drainage and steep island catchments alike. Warnings for Oshima Town preceded the heaviest Kanto rain by more than a day, and the forecast restrengthening on 22 September meant response postures had to hold after the closest approach. For Atlantic forecasters, the continued absence of a hurricane into late September frames seasonal verification and resource allocation questions that will persist even if Fay remains weak.
