Typhoon Koto (33W / Verbena) – Tropical Cyclone Advisory #6: 1200 UTC 26 November 2025

…Koto rapidly intensifies into a typhoon… …Forecast to move erratically and fluctuate in intensity during the next few days…

Current storm information:

• Position: 12.6°N 115.2°E

• Movement: WNW at 10 knots (205 km/h)

• Intensity: 65 knots (120 km/h)

• Central pressure: 975 hPa

Trend:

• Some additional strengthening is possible during the next 24 hours.

Discussion:

Although it may not look like it based on conventional satellite imagery, Koto appears to be rapidly intensifying. Microwave satellite imagery from NOAA-21 ATMS indicates that the partial eye feature that was present before has closed off into a complete eyewall, although convection remains strongest on the western side. Despite cooler, more stable air associated with the northeast monsoon continuing to impinge upon Koto’s poleward outflow channel, Koto is sporting a compact yet somewhat ragged central dense overcast with the eye intermittently visible. Most of the convection is displaced to the west of the center, which is a bit unusual because CIMSS shear analysis suggests shear is fairly light. Dvorak estimates are a consensus T4.0, and a Sentinel-1 SAR pass indicated 10-minute winds of 56 kts in the northwest quadrant. Based on these data, the intensity is increased to 65 kts and Koto is now a typhoon.

The forecast is unchanged, but that isn’t really a good thing because it is also quite difficult. For the time being, Koto is in a favorable environment with relatively warm SSTs and low shear, slightly offset by the northeasterly cold surge flow. Most of the model guidance suggests that Koto will continue to strengthen for another day or so as it moves slowly and erratically west-northwestward. By Friday, cooler SSTs and a greater interaction with the cold surge should cause some weakening. Meanwhile, the steering regime is expected to become complicated as Koto becomes trapped between a ridge to the northeast and northerly to northeasterly upper-level flow associated with Tropical Cyclone Senyar in the Malacca Strait. There is a ridiculous amount of spread among the models, with some tracks showing Koto meandering in the central South China Sea (mainly the GFS deterministic and ensemble models), some showing it moving over Vietnam by the end of the forecast period (ECMWF ensemble, HAFS-A and HWRF), and still others showing it moving southwestward as it interacts with Senyar and possibly even pulling Senyar into the Western Pacific basin, which I believe is unprecedented. 

Needless to say, the track and intensity forecast are currently quite low confidence, and Koto is currently forecast to more or less meander and fluctuate in intensity during the next few days.

Forecast positions and maximum winds (1-min)

• 000 hrs: 12.6°N 115.2°E – 65 kts 120 km/h 

• 012 hrs: 12.9°N 114.2°E – 70 kts 130 km/h

• 024 hrs: 12.5°N 113.6°E – 70 kts 130 km/h 

• 048 hrs: 12.4°N 112.6°E – 65 kts 120 km/h 

• 072 hrs: 13.1°N 112.5°E – 55 kts 100 km/h 

• 096 hrs: 13.8°N 112.2°E – 50 kts 95 km/h 

• 120 hrs: 13.4°N 110.8°E – 50 kts 95 km/h 

One last thing… 

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