Tropical Storm Peipah (21W) – Tropical Cyclone Advisory #4: 0000 UTC 4 September 2025

…Depression becomes Tropical Storm Peipah just south of Kyushu…

Current storm information:

• Position: 29.8°N 131.1°E

• Movement: N at 16 knots (25 km/h)

• Intensity: 35 knots (65 km/h)

• Central pressure: 1002 hPa

Trend:

• Little change in strength is forecast during the next 24 hours.

Discussion:

The depression has continued to get somewhat better organized since the previous advisory. The bands of convection wrapping into the circulation center have coalesced into a ragged central dense overcast feature. Radar data suggests that a partial eyewall feature is present, but wraps only about a quarter of the way around the center. Despite the improvement in the system’s structure, most of the convection is spreading across a stationary front draped along the southern coast of Japan (with a weak, non-tropical low pressure area located along it to the south of the Kanto Plain). Dvorak estimates range from T2.0 to T2.5, with CIMSS ADT and AiDT estimating 34 and 38 kts respectively. A blend of these estimates yields an intensity of 35 kts and JMA has upgraded the system to Tropical Storm Peipah.

Peipah is currently approaching southern Kyushu. It is already interacting with a non-tropical low to its east-northeast and rounding the northwestern periphery of the subtropical ridge, so it appears that Peipah will pass just to the southeast of Kyushu later today. No significant change in strength appears likely before Peipah moves over Shikoku or southern Honshu on Friday morning, then turns eastward. By Saturday, Peipah will likely be absorbed by the non-tropical low pressure area just southeast of Japan, so the track ends after 48 hours.

Forecast positions and maximum winds

• 00 hrs: 29.8°N 131.1°E – 35 kts

• 12 hrs: 31.7°N 131.9°E – 35 kts

• 24 hrs: 33.8°N 134.1°E – 35 kts inland

• 48 hrs: 33.7°N 143.7°E – 35 kts Post-tropical/extratropical

• 72 hrs: Absorbed by extratropical low