Tropical Storm Tapah (22W/ex-Lannie) – Tropical Cyclone Advisory #4: 0000 UTC 7 September 2025

…Tapah strengthening over the South China Sea…

Current storm information:

• Position: 18.3°N 114.3°E

• Movement: W at 5 knots (10 km/h)

• Intensity: 45 knots (85 km/h)

• Central pressure: 994 hPa

Trend:

• Some strengthening is forecast during the next 24 hours.

Discussion:

Tapah is getting better organized. Convective banding has become much better defined during the past several hours and is wrapping into the low-level circulation center. There does seem to be some mid-level subsidence affecting the system, however, as the center has become partially exposed during the past couple of hours. In spite of this, microwave satellite image suggests that Tapah is establishing an inner core with a partial eyewall feature, although the partial eyewall is not vertically aligned over the surface center. The intensity is increased to 45 kts based on consensus T3.0 Dvorak fixes from PGTW, KNES, and RJTD. 

Tapah has slowed down considerably during the past 12 hours or so as it responds to a change in steering currents induced by an upper-level trough pushing across China and weakening the ridge. As the ridge weakens, Tapah should gradually turn toward the northwest and move toward southern China. The environment is expected to be conducive for strengthening, and in fact, CIMSS AI-RI and RAMMB RIPA rapid intensification guidance show a moderate chance of rapid intensification during the next 24 hours. Tapah will likely become a typhoon before it makes landfall on Monday, and the wind values given below may be a bit conservative. Steady to rapid weakening is forecast after landfall and Tapah should decay into a trough of low pressure over south central China by Wednesday.

Forecast positions and maximum winds

• 00 hrs: 18.3°N 114.3°E – 45 kts

• 12 hrs: 19.5°N 113.5°E – 55 kts

• 24 hrs: 21.0°N 112.4°E – 65 kts

• 36 hrs: 22.3°N 110.9°E – 35 kts inland

• 48 hrs: 23.2°N 109.5°E – 25 kts inland

• 72 hrs: Dissipated