Tropical Storm Peipah (#21W) – Tropical Cyclone Advisory #5: 1200 UTC 4 September 2025

Center of Peipah over the Bungo Channel and about to move over southwestern Shikoku.

Author

Will Weaver
September 04, 2025

…Center of Peipah over the Bungo Channel and about to move over southwestern Shikoku…

Himawari-9 infrared satellite image (Weathernerds)

Current storm information:

  • Position: 32.7°N 132.1°E

  • Movement: NNE at 14 knots (25 km/h)

  • Intensity: 35 knots (65 km/h)

  • Central pressure: 998 hPa

Trend:

  • Little change in strength is forecast during the next 24 hours, and Peipah will likely become a post-tropical cyclone on Saturday.

Watches and warnings:

  • There are no land-based watches or warnings in effect.

Hazards affecting land:

  • Heavy rain and gusty winds are likely to continue over portions of Kyushu and Shikoku through late tonight. These conditions will spread over southern Honshu, including the Kanto Plain, on Friday. U.S. military interests can get additional information from the Stars & Stripes Pacific Storm Tracker: https://www.stripes.com/theaters/asia_pacific/storm_tracker/

Discussion:

Composite radar image (CyclonicWx)

Peipah passed just to the southeast of Kyushu during the past several hours, and its center is now located over the southern entrance of the Bungo Channel. At first glance, one would think the storm has gotten better organized, and it does consist of a central dense overcast with very intense convective cloud tops obscuring a fairly well defined circulation center. However, radar data and microwave satellite imagery indicate that Peipah is in the early stages of extratropical transition, with most of the convection displaced to the north and east of the center. There are also indications that cold and warm fronts are beginning to develop fairly close to Peipah’s center, and this is noticeable in temperature observations in the region. Although Dvorak estimates range from T2.5 to T3.0 with slightly lower CIMSS ADT and D-PRINT estimates, surface observations suggest Peipah has not strengthened, and so the intensity remains 35 kts.

The forecast remains unchanged, though there are indications that changes may soon be needed. Peipah is currently embedded in southwesterly flow associated with a subtropical ridge to the southeast, and it should move generally northeastward during the next day or so. Given the environment of moderate shear and land interaction, Peipah is unlikely to change significantly in strength during that time. Model guidance is beginning to suggest that Peipah will not be absorbed by the non-tropical low developing to its northeast, but will instead be left behind to meander in the north Pacific after moving away from Japan. The current forecast will continue to call for absorption after Saturday, but it is possible Peipah could be around for much longer, though if it isn’t absorbed by the low, highly unfavorable conditions will likely result in Peipah becoming post-tropical anyway.

Forecast positions and maximum winds

  • 00 hrs: 32.7°N 132.1°E – 35 kts

  • 12 hrs: 34.0°N 134.3°E – 35 kts inland

  • 24 hrs: 34.5°N 139.9°E – 35 kts Post-tropical/extratropical

  • 48 hrs: 32.8°N 149.9°E – 35 kts Post-tropical/extratropical

  • 72 hrs: Absorbed by extratropical low

JMA forecast map