Tropical Storm Nari (06W) – Tropical Cyclone Advisory #5: 0000 UTC 13 July 2025

…Tropical Storm Nari accelerating northward to the east of the Ogasawara Islands…

Current storm information:

• Position: 26.5°N 142.5°E

• Movement: N at 7 knots (10 km/h)

• Intensity: 35 knots (65 km/h)

• Central pressure: 998 hPa

Trend:

• Some strengthening is forecast during the next 24 hours.

Watches and warnings:

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

Hazards affecting land:

• Interests along the eastern coast of Honshu and in the Aleutian Islands should monitor the progress of this system.

Discussion:

Tropical Storm 06W – now named Nari by JMA – is a little bit better organized this morning. Although the system continues to be sheared and most of its convection is displaced to the south and east of the center due to interaction with an upper-level trough, the low-level and mid-level centers are a little bit closer together and the convective banding is better defined. Microwave satellite imagery also suggests that the banding is beginning to wrap more tightly into the mid-level center, and it is possible the low-level center may be in the process of reforming near the mid-level one. The intensity is held at 35 kts, despite Dvorak estimates ranging from T2.5 to T3.0 and a slightly higher SATCON estimate.

Nari is continuing to accelerate northward due to increasingly strong southerly wind flow associated with an unseasonably strong subtropical ridge to the east and the upper trough to the northwest. This acceleration is expected to continue today, to the point that by this time tomorrow, Nari will already be passing east of Honshu. Despite this quick movement, it is possible that Nari could strengthen while it remains over warm waters, and it is expected to reach peak intensity in about 24 hours. By tomorrow afternoon, however, Nari will be moving over rapidly cooling waters and into an area of very strong westerly shear, and this should result in Nari rapidly transitioning into an extratropical low near Hokkaido by Tuesday. Post-tropical Nari is then forecast to turn sharply eastward as it rounds the subtropical ridge. By Thursday, the post-tropical cyclone could regain some strength as it approaches the Aleutian Islands and exits the basin.

Forecast positions and maximum winds

• 00 hrs: 26.5°N 142.5°E – 35 kts

• 12 hrs: 29.6°N 142.6°E – 45 kts

• 24 hrs: 33.8°N 142.0°E – 50 kts

• 48 hrs: 42.9°N 143.9°E – 40 kts Post-tropical/extratropical

• 72 hrs: 48.5°N 154.5°E – 30 kts Post-tropical/extratropical

• 96 hrs: 47.5°N 168.0°E – 30 kts Post-tropical/extratropical

• 120 hrs: 48.0°N 178.5°W – 40 kts Post-tropical/extratropical