Post-Tropical Cyclone Peipah (#21W) – Tropical Cyclone Advisory #7 (FINAL): 1500 UTC 5 September 2025

…Peipah rapidly becoming a powerful post-tropical cyclone as it moves away from Japan… …This is the last advisory…

Current storm information:

• Position: 35.8°N 144.7°E

• Movement: ENE at 30 knots (55 km/h)

• Intensity: 55 knots (100 km/h)

• Central pressure: 990 hPa

Trend:

• The post-tropical cyclone is forecast to strengthen a little during the next 24 hours.

Discussion:

Peipah continues to generate a great deal of deep convection near and to the east of its circulation center. However, a look under the hood indicates that the cyclone is no longer fully tropical. Peipah’s convection is spreading east-northeastward along a frontal boundary, and there now appear to be well-defined warm and cold fronts attached to its center. The circulation center is also on the southwestern edge of the main area of convection and has become sharply elongated, and ASCAT data indicates the wind field has expanded greatly to the south and east. Although it is not completely extratropical just yet, Peipah is well on its way to becoming a strong warm seclusion extratropical cyclone and should become one during the next few hours. The intensity is increased quite a bit to 55 kts, hedged between tropical Dvorak fixes of T3.0 to T3.5 from KNES and RJTD, and a Miller-Lander extratropical technique fix of XT4.0 from PGTW, and this estimate is consistent with the scatterometer data.

Peipah is currently in a very baroclinically favorable environment with warm SSTs combined with very cool air filtering in from the north, along with warm air advection from another trough over the Kuril Islands. These factors should cause some short-term strengthening as the post-tropical cyclone continues racing east-northeastward, and Peipah could become a hurricane force low early on Saturday. By Sunday, however, another extratropical low pressure area is expected to strengthen to Peipah’s northeast, which will rob it of its baroclinic forcing and cause Peipah to rapidly weaken. Although Peipah will also lose its frontal characteristics in the process, the environment will not be favorable for it to transition back into a subtropical or tropical cyclone, and Peipah will likely dissipate within the new low’s cold front late on Monday.

This is the last advisory on Peipah.

Forecast positions and maximum winds

• 00 hrs: 35.8°N 144.7°E – 55 kts

• 12 hrs: 36.2°N 149.9°E – 65 kts Post-tropical/extratropical

• 24 hrs: 36.4°N 155.9°E – 55 kts Post-tropical/extratropical

• 48 hrs: 38.4°N 163.0°E – 45 kts Post-tropical

• 72 hrs: 41.5°N 171.0°E – 35 kts Post-tropical

• 96 hrs: Dissipated