Tropical Storm 08W - Tropical Cyclone Advisory #1, 1200 UTC 15 July 2025

…Tropical storm along the coast of Honshu… …Expected to be very short-lived…

Discussion:

Invest 95W, which has never looked particularly pretty, developed a small core of tropical storm force winds within the last 12 hours. Since the system had a fairly well defined but elongated circulation center, JTWC upgraded it to a tropical storm at 0000 UTC – this is a rare case of a system designated as a tropical storm by JTWC and as nothing by JMA.

Tropical Storm 08W is a very poorly organized system due to being squeezed within a very narrow upper-level trough in the wake of Post-Tropical Cyclone Nari far to the northeast. Most of the convection is displaced to the south of the center. Composite radar imagery from Japan indicates that the circulation is very small with no indications of an inner core. Although Dvorak and D-PRINT fixes are not particularly impressed with the system, CIMSS ADT and AiDT estimates are 41 and 44 kts respectively, and surface observations from Japan suggest the winds are about 40 kts.

TS 08W isn’t going to be around for very long. As Post-Tropical Cyclone Nari moves away, southerly wind shear is forecast to increase dramatically very soon. This shear, combined with land interaction and rapidly cooling SSTs off the eastern coast of Honshu, is expected to cause dramatic weakening, and the few models that actually pick up 08W indicate dissipation within about 24 hours or so. The remnants of 08W are forecast to be absorbed by a deep extratropical low pressure system over the Sea of Japan later on Wednesday, the same one that absorbed the remnants of Subtropical Depression 07W.

Forecast positions and maximum winds:

• 00 hrs: 36.5°N 141.0°E – 40 kts

• 12 hrs: 40.5°N 142.1°E – 35 kts

• 24 hrs: 44.5°N 142.5°E – 30 kts Post-tropical/extratropical

• 48 hrs: Dissipated