Tropical Storm Koto (33W / Verbena) – Tropical Cyclone Advisory #4: 1200 UTC 25 November 2025

…Depression strengthens into Tropical Storm Koto as it approaches northern Palawan…

Current storm information:

• Position: 11.0°N 120.2°E

• Movement: WNW at 9 knots (15 km/h)

• Intensity (1-min): 40 knots (75 km/h)

• Intensity (10-min): 35 knots (65 km/h)

• Central pressure: 996 hPa

Trend:

• Some strengthening is forecast during the next 24 hours.

Discussion:

Tropical Depression 33W has gotten quite a bit better organized since the previous advisory. Convection near the circulation center has consolidated into a very compact central dense overcast, with well-defined dual outflow channels. The convection within the CDO is quite intense with very cold (-80°C) cloud tops, and microwave satellite imagery indicates that spiral banding is wrapping into the center and beginning to form into an inner core with a partial eye feature. Scatterometer data suggests that the system is now producing tropical storm force winds, and the intensity is increased to 40 kts, hedged between Dvorak fixes ranging from T2.0 to T3.0 and much higher automated estimates ranging from 41 to 47 kts. As a result, JMA has upgraded the system to Tropical Storm Koto.

The forecast has become a bit tricky owing to Koto’s very small size. Although much of the guidance only indicates gradual strengthening as Koto moves across Palawan and into the South China Sea, AI-RI and RIPA rapid intensification guidance indicates a high probability of rapid intensification during the next 24 to 36 hours. The environment appears to be conducive for strengthening during the next 2 to 3 days or so, with low shear and fairly warm SSTs, and the GFS, HAFS-A, and a good number of ECMWF and Google DeepMind ensemble members bring Koto to typhoon strength by Thursday. Therefore, the forecast indicates Koto peaking at around 65 kts by that point, and this is higher than the JTWC forecast.

After Thursday, Koto will be moving over cooler waters and interacting with the northeast monsoon, and this should result in some weakening. In addition, steering currents are expected to collapse as the subtropical ridge to the north weakens, and this will cause Koto to begin moving erratically toward the northwest through the end of the forecast period. The weakening of the ridge will also weaken the northeast monsoon, and so fluctuations in intensity are likely over the weekend. Due to a huge amount of spread among the models, confidence in the late portion of the forecast is fairly low. It is also unclear what effect, if any, newly-formed Tropical Cyclone 04B near the Malay Peninsula could have on the steering regime.

Forecast positions and maximum winds (1-min)

• 000 hrs: 11.0°N 120.2°E – 40 kts 75 km/h 

• 012 hrs: 12.3°N 117.6°E – 50 kts 95 km/h

• 024 hrs: 12.7°N 115.5°E – 60 kts 110 km/h 

• 048 hrs: 12.3°N 113.1°E – 65 kts 120 km/h 

• 072 hrs: 12.3°N 111.9°E – 55 kts 100 km/h 

• 096 hrs: 13.2°N 111.1°E – 45 kts 85 km/h 

• 120 hrs: 14.5°N 110.6°E – 50 kts 95 km/h 

One last thing… 

Do you like what you see? Please consider sending a tip via Ko-fi! I wear a lot of hats between a day job, being a photographer, and being a worldwide weather enthusiast, and while I will never put any of my content behind a paywall (paywalls kind of defeat the purpose of this blog/newsletter/thingy), your tips definitely help! You can send a tip via the following link: https://ko-fi.com/willweaverrva