Severe Tropical Storm Sinlaku (04W) – Tropical Cyclone Advisory #21: 1200 UTC 18 April 2026

…Sinlaku weakens to a tropical storm…
…Expected to become post-tropical on Sunday…

Current storm information:

• Position: 24.2°N 147.2°E

• Movement: NNE at 10 knots (20 km/h)

• Intensity: 60 knots (110 km/h)

• Central pressure: 979 hPa

Trend:

• Steady weakening is forecast during the next 24 hours, and Sinlaku will likely become a post-tropical cyclone on Sunday.

Discussion:

Sinlaku is rapidly losing tropical characteristics. The tropical cyclone has moved over much cooler waters (about 24°C) and into an area of very strong westerly wind shear. Much of Sinlaku’s structure has been ripped apart as a result; most of the CDO convection has dissipated, and the only convection remaining is displaced well to the east of the center. The center itself is also completely exposed and embedded in a very dry air mass. Despite the less than tropical convective structure, Sinlaku is still a tropical cyclone with a deep warm core based on cyclone phase diagrams. Scatterometer and SAR data suggests that Sinlaku is still producing winds of 50 to 60 kts, primarily to the east of the center, and the intensity is set to 60 kts.

The environment is expected to become even less favorable as Sinlaku continues moving northeastward through the night and into tomorrow, with even stronger shear and cooler SSTs ahead. A developing frontal system moving off the coast of Japan is expected to quickly overtake Sinlaku by Sunday evening or Monday, which will likely cause it to complete extratropical transition and become a post-tropical cyclone. Post-tropical Sinlaku should become absorbed by the frontal boundary soon after.

Forecast positions and maximum winds (1-min)

• 000 hrs: 24.2°N 147.2°E – 60 kts 110 km/h 

• 012 hrs: 26.5°N 149.8°E – 50 kts 95 km/h 

• 024 hrs: 28.3°N 153.7°E – 45 kts 85 km/h 

• 048 hrs: 30.0°N 163.7°E – 45 kts 85 km/h POST-TROPICAL/EXTRATROPICAL

• 072 hrs: ABSORBED BY LARGER EXTRATROPICAL LOW