Severe Tropical Storm Koto (33W) – Tropical Cyclone Advisory #9: 0000 UTC 28 November 2025

Koto weakening rapidly as it moves very slowly westward...

Author

Will Weaver
November 27, 2025

…Koto weakening rapidly as it moves very slowly westward…

GEO-KOMPSAT-2A visible satellite image (CyclonicWx)

Current storm information:

  • Position: 12.4°N 113.1°E

  • Movement: W at 3 knots (5 km/h)

  • Intensity: 55 knots (100 km/h)

  • Central pressure: 988 hPa

Trend:

  • Gradual weakening is forecast during the next 24 hours.

Watches and warnings:

  • There are no coastal watches or warnings in effect.

Hazards affecting land:

  • Interests in Vietnam should monitor the progress of this system.

Discussion:

Koto has very rapidly lost most of its convection over the past few hours as southeasterly shear forces cooler, drier air associated with the northeasterly cold surge into its circulation. Koto now consists of a fully exposed swirl of low clouds with a single fragmented band of convection displaced well to the north and west of the center. Despite the loss of core convection, the mid-level outflow seems to be robust enough to sustain that band. Satellite-based estimates of Koto’s intensity are dropping about as quickly as the Dvorak rules allow, and the intensity is lowered to a potentially generous 55 kts based on consensus T3.5 Dvorak fixes.

The forecast is generally unchanged - Koto is expected to continue moving slowly and erratically toward the west during the next few days as steering currents remain weak. Model guidance suggests that convection could come and go during that time, especially as Koto begins to interact with a recently regenerated Tropical Depression Senyar to its southwest. Koto is expected to absorb Senyar’s circulation on Tuesday, but this interaction combined with strong shear and cool SSTs will likely accelerate the weakening trend. By the end of the forecast period on Wednesday, Koto should finally move inland over southern Vietnam and weaken to a tropical depression.

Forecast positions and maximum winds (1-min)

  • 000 hrs: 12.4°N 113.1°E – 55 kts 100 km/h 

  • 012 hrs: 12.7°N 112.7°E – 50 kts 95 km/h

  • 024 hrs: 13.1°N 112.1°E – 45 kts 85 km/h 

  • 048 hrs: 13.9°N 112.2°E – 40 kts 75 km/h 

  • 072 hrs: 14.0°N 111.6°E – 40 kts 75 km/h 

  • 096 hrs: 13.2°N 110.2°E – 35 kts 65 km/h 

  • 120 hrs: 13.0°N 108.1°E – 25 kts 45 km/h inland

JMA forecast map