Tropical Storm Kalmaegi (31W, formerly 98W) – Tropical Cyclone Advisory #2: 1200 UTC 1 November 2025

…Depression strengthens into Tropical Storm Kalmaegi as it moves away from Yap…

Current storm information:

• Position: 10.3°N 137.0°E

• Movement: WNW at 12 knots (20 km/h)

• Intensity: 35 knots (65 km/h)

• Central pressure: 1000 hPa

Trend:

• Some strengthening is forecast during the next 24 hours.

Discussion:

The tropical depression, now Tropical Depression 31W per JTWC, is continuing to get better organized as it turns west-northwestward and moves away from Yap State. Although the convective banding is not as clear cut as it was around the time of the previous advisory, the convection as a whole has consolidated into a solid overcast feature. The convective mass is slightly displaced to the south and east of the circulation center, though it is in the process of expanding due to increasingly good poleward outflow. Unfortunately there have not been any recent microwave imager passes of a high enough resolution to determine TD 31W’s internal structure. Dvorak estimates range from T2.0 to T2.5 while automated CIMSS ADT, AiDT, and D-PRINT estimates suggest that the system is now a tropical storm, and JMA has upgraded it to Tropical Storm Kalmaegi with winds of 35 kts.

The track forecast is unchanged but the intensity forecast remains highly problematic and of low confidence. Kalmaegi is embedded within strong easterly surface flow and is forecast to move generally westward through the end of the forecast period, crossing over the Visayas on Tuesday before reaching the South China Sea by midweek. There continues to be an enormous amount of spread among the intensity guidance, with the GFS and ECMWF ensembles suggesting only modest strengthening prior to reaching the Philippines, while the HAFS-A, the deterministic GFS, and Google DeepMind ensemble indicate significantly more strengthening. It seems that the rate of intensification is dependent on what happens with invest area 99W to the east - if 99W develops, it will likely produce shear that would put a cap on Kalmaegi’s intensification process. The models seem to be backing off on 99W developing, and in fact the rapid intensification guidance (AI-RI and RIPA) indicate a high probability of RI, with RIPA indicating a 60% chance of an increase of 65 kts in the next 72 hours. At this point, the intensity forecast prior to reaching the Philippines remains uncertain but the wind values given below are higher than the JMA and JTWC forecasts and indicate Kalmaegi becoming a typhoon.

After Kalmaegi crosses the Visayas and Palawan and enters the South China Sea, the model guidance almost unanimously indicates another round of rapid strengthening, as the environment will likely be quite favorable due to low shear and very warm SSTs that have not been cooled by northeasterly cold surges. As a result, Kalmaegi is likely to be an intense typhoon by the end of the forecast period, and interests in Vietnam need to monitor its progress.

Forecast positions and maximum winds

• 000 hrs: 10.3°N 137.0°E – 35 kts

• 012 hrs: 11.0°N 135.8°E – 45 kts

• 024 hrs: 11.4°N 133.1°E – 60 kts

• 048 hrs: 11.2°N 127.9°E – 90 kts

• 072 hrs: 11.4°N 122.7°E – 85 kts inland over Panay

• 096 hrs: 12.3°N 117.9°E – 100 kts

• 120 hrs: 13.5°N 112.8°E – 115 kts