Tropical Storm Peipah (2025)

On September 2, 2025 at 12:00 UTC (21:00 JST), the Japan Meteorological Agency (JMA) began monitoring a newly formed tropical depression located approximately 430 nmi (800 km) southeast of Naha, Okinawa.^[5] At 08:00 PHT (00:00 UTC) on September 3, the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA) began issuing advisories on the system after it entered the Philippine Area of Responsibility, assigning it the local name Kiko.^[6] Later that same day, the Joint Typhoon Warning Center (JTWC) issued a Tropical Cyclone Formation Alert (TCFA) for the disturbance, noting the likelihood of tropical cyclogenesis within 24 hours due to improving environmental conditions, including warm sea surface temperatures and decreasing vertical wind shear.^[7]

At 15:00 UTC, the JTWC upgraded the system to a tropical depression, assigning it the designation 21W.^[8] During the early hours of September 4, the JMA upgraded the system to a tropical storm, assigning it the international name Peipah. At this point, the system was tracking north-northeastward along the northwestern periphery of the subtropical ridge, aided by favorable upper-level divergence and warm oceanic waters.^[9][10] Peipah later curved eastward under the influence of an approaching mid-latitude trough and began to affect the southern coastline of western Japan.

At 01:00 JST (16:00 UTC) on September 5, the system made landfall over Sukumo in Kōchi Prefecture, bringing strong winds and heavy rainfall to parts of Shikoku and the surrounding areas.^[11] Shortly afterward, at 09:00 JST (00:00 UTC), Peipah made a second landfall over northern Wakayama Prefecture, skimming past the Kii Peninsula as it continued its east-northeastward track.^[12] Following these landfalls, the JTWC reported that Peipah had begun undergoing extratropical transition as it began to acquire characteristics of a mid-latitude cyclone. The system exhibited hybrid features, with a partially cold-core structure and asymmetric convection, while accelerating over cooler waters to the east.^[13] Satellite imagery during this period revealed that the system’s deep convection was being significantly sheared by 25–30 knots of vertical wind shear associated with a nearby shortwave trough located to its northwest.^[13] Peipah later completed its transition and became an extratropical low, causing both JMA and JTWC to cease advisories at 15:00 UTC and 12:00 UTC respectively.^[14]

In Japan, a heavy rain warning was issued by the JMA, urging residents to remain vigilant due to the increased risk of landslides and flooding.^[15] In response to the approaching storm, the West Nippon Expressway Company announced the closure of several road sections, particularly along the Higashikyushu Expressway.^[16] Railway operators from thrEast Japan Railway Company have announced delays, suspensions, and cancellations as the storm affected its service.^[17]

Meanwhile, local fishermen secured their vessels and implemented safety measures in preparation for the storm.^[18] In Miyazaki Prefecture, authorities issued a tornado advisory, warning of a heightened risk of tornado activity associated with the storm's outer bands.^[19] The government ordered 660,000 people to evacuate.^[20] Operations of the Tokaido Shinkansen bullet-train service were partly suspended.^[21]

• Weather of 2025
• Tropical cyclones in 2025
• Other storms named Peipah
• Other storms named Kiko
• Tropical Storm Zia (1999) - made landfall in a similar area
• List of Japan tornadoes