Tropical Storm Koto (33W) – Tropical Cyclone Advisory #11: 0000 UTC 29 November 2025

…Koto continuing to move little and gradually weaken…

Current storm information:

• Position: 13.1°N 112.2°E

• Movement: NW at 3 knots (5 km/h)

• Intensity: 45 knots (85 km/h)

• Central pressure: 996 hPa

Trend:

• Gradual weakening is forecast during the next 24 hours.

Discussion:

Koto continues to gradually weaken as it goes nowhere fast well off the eastern coast of Vietnam. The storm consists of an irregularly shaped area of convection displaced to the north and west of a mostly exposed low-level circulation center. The convection has little in the way of structure, and there is little in the way of banding present. Scatterometer data suggests the circulation has spun down somewhat, with only a small area of 40 to 45 kt winds located near the center. Given this data and consensus Dvorak fixes of T3.0, the intensity is lowered to 45 kts.

Although the shear has relaxed somewhat during the past 12 to 24 hours, marginal SSTs and interaction with the northeasterly cold surge combined with its slow movement should result in a continued slow weakening trend during the next few days. Some weak southerly upper-level flow associated with Tropical Depression Senyar should nudge Koto a bit to the north during the next couple of days. By Monday, another northeasterly monsoon surge combined with interaction with an approaching Senyar will result in a sharp turn toward the southwest. Most of the model guidance suggests that Koto will weaken rapidly as it approaches Vietnam and absorbs Senyar, and Koto is now forecast to dissipate shortly after reaching the Vietnam coast on Wednesday.

Forecast positions and maximum winds (1-min)

• 000 hrs: 13.1°N 112.2°E – 45 kts 85 km/h 

• 012 hrs: 13.4°N 112.1°E – 45 kts 95 km/h

• 024 hrs: 13.7°N 112.2°E – 45 kts 85 km/h 

• 048 hrs: 14.3°N 112.2°E – 45 kts 85 km/h 

• 072 hrs: 13.8°N 110.9°E – 35 kts 65 km/h 

• 096 hrs: 13.2°N 109.6°E – 30 kts 55 km/h 

• 120 hrs: Dissipated